The Science of Animal Breeding in Britain

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THE SCIENCE OF ANIMAL BREEDING INBRITAIN: A SHORT HISTORY

This essay is a simplified out comprehensive account of Britishwork in thc field of animal breeding from the earliest attempts , byfarrners, to the most recent scientifically controlled experiments.DI'. F. H. A. Marshall, Fellow and formerly Vice-Master ofChrist's College, Cambridge, is a leading British expert on Agri

cultural Physiology, and no Icss well known as an authority OIlsexual physiology and the physiology of reproduction. From Ig05lo Ig08 he was Lecturer on the Physiology of Reproduction atEclinburgh Univcrsity, and from 1908 te 1919 Lecturer onAgricultural Physiology at Cambridge, where he bccarne Rcader,which post he he Id until 19+3. From 1930 to 193+ he was Directorof the Anima l Nut ri tion Instituto at Cambridge. From 1933 to1935 he scrved on the Council of the Royal Society and wasawarded the Royal modal in 19+0. In 1927 he was sent to AIgeriaby the Ministry of Agriculture on a delcgation to repo rt on Dr.Voronoff''s gland-grafting experimenrs,Dr. John Hammond is Reader in Agricultural Physiology atCambridge University. He is an authority on cattle breeding, andthe author of many papers on ferti li ty, growth, milk and meatproduction.

Sciencc m Britain


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BR lTISH COUNCIL 'S CODE N."'-'''IE : ANIMALS (ENGLISH)

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Top leJt: ] . ass E ioart, dJ51-1933Bol/om Hri/!ialll Bateson; 1861-1926 'To ]: right: Walter Heape, 1855-1929Boitom right: ThomasBailoui Wond, 186.9-1929


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y ~ ' 7 L ~ t: i: "Jo ~ ~ / W ' 1THE SCIENCE F ANIMALBREEDING IN BRITAIN

A Short History

BY

F. H. A. MARSHALLC.B.E., Se.D.) LL.D.) F.R.S.A l ~ D

jOHN HAMMONDM.A.) D.Se. F.R.S.

ILLUSTRATED

Published forTHE BRITISH COUNCIL

BY LONGMANS, GREEN AND CO .LONDON NEW YORK TORNT


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CONTENT S

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lFrontispieceFacing page 6

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I NTRODUCTORYT nz P RE-SClENTlFIC P ER lODFRA)iCIS G ALTON] . COSSAR E WART\VALT ER I-f EAP E

G E ~ I:-i C A m R l D G - \ V I I A M BATESONG EN ETICS IN E DI NllURG I I -F . A. E . CREW .ANlMAL PHYSIOLOGY IN C\MllRlDGEBIBLIOGRAPHY

11.. 1..USTRATIONSJ. COSSAR EWART\ VALTER H EAPE\ VILLIAM DATESONTHOM:\ S BARLOW "\VOODEVOLUTlON IN T HE S HO RTIJORN BREED

R T A N C E OF H OR NS AND FACE COLOUR IN SREEPFO ET,\ L ATROPI-IY IN PIGSSHETU.ND-SmRE C ROSSES .G ROWTH CRANGES IN T H E PIG .

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THE SCIENCE OF ANIMAL BREEDING INBRITAIN: A SHORT HISTORY

'Breed ing is the greatest industry to which Science has never yet bc .:applied.' These words were spoken to the Zoological Section of theBritish Association by William Bateson in his presidential address to thatbody in 1904. And he added, referring especially to the study of hercdityand variation, that the practical economic value of such application 'willbe found of extraordinary use'. Bateson's words were endorsed andextended by Walter Heape in a work on The Breeding Industry published in1906, and he remarked that the study ofthe physiology ofbrecding wouldbe of equal importance when applied to such subjects as animal fertilityand the factors controlling it.

It may be wondered how in the absence ofbiological research as appliedto the production of domestic animals Britsh breeders obtained suchremarkable results. For it is undeniable that very great success wasachieved and in all classes of stock. I t has been truly said that with theexception of the Perchern and Belgian horses, the Holstein-Friesian andSwiss cattle and the Merinos sheep, almost all the important classes ofdomestic animals widely spread throughout the temperate zones of theworld are of British origino This is the case also of many othcr animalswhich have become separate breeds, sch as the American Trotter, whichis based on the English Hackney.The explanation of this success is twofold. In the first place the selectionof suitable individual animals for perpetuating their kind is very largelyan art and not a science, and the capacity to practise i t depends uponcertain attributes of hand and eye which sorne men in this country havepossessed to a remarkable degree. And, secondly, in spite of what Bateson


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2 The Application ofScience lo AnimalBreedingand Heape have said to the contrary, many of the mcthods adoptcd bythe breeder were essentialIy though unconsciously scientific.

TH E PRE-SCIENTIFIC P ER I ODThe first attempts to bring about improvement in domestic animals were

rnade by prvate individuals without any support from the Governmentor from scientific or agricultural societies. Among the most successful ofthese was Robert Bakewell, whose work led to the development of thefamous Longhom cattle (1750) and the Leicester sheep (1755). JohnEllman, who brcd the Southdown sheep (1778), and Charles and RobertColling, who founded the breed of Shorthorn cattle (1780), supply otherwell-known instances. Their methods were those of what Darwin calIed'artificial selection'; that is to say, they chose thc best animals they couldget for the purposes they had in view and then proceedcd to breed fromthem, continuing the process in succeeding generations. In other words,having decided on what types to aim at , they concentrated on thoseherds and flocks whose individuals had the desired characters. Thisusually involved clase breeding and even intensive inbreeding, which laterscientific work has shown in certain cases to be harmfuI. Essentially thesame methods were adopted by breeders of horses, and in the case ofthe Thoroughbred the performance tests ofthe racecourse became the chiefguide in the selection ofanimals to breed from, and thesewerc duly recorded.

With cattle also it was soon seen that in order to maintain the irnprovement that had been reached, it was necessary to prevent 'dilution ofblood' in strains that had been distributed about the country and consequently were in danger of being contaminated by crossing with inferioranimals, To avoid this herd-books were insti tuted, and in these the pedigrees of the breeding animals which traced back to the original super iorindividuals were all recordcd. The earliest of these herd-books was Coa tes'Herd-book for the Shorthom Breed and the first volume was published in 1822.The institution ofherd-books led to the formation ofbrecd societies whichissued thcrn, and in this way standards of quality were set up and itbecame the aim of breeders to attain to these standards in the anirnalswhich they bred. Moreover, the process of artificial selection was continued within the families of animals entered in the herd-books, and so


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" The Pre-scentific Perod 3atternpts were made, and usually successfuIly, to keep and even toimprove the excellence of type already reached, Again, as cornmercialrequirernents changed, or even in response to the caprices of fashion, thestandards successfully set up also changed as a result of selection withinthe strains. Thus, by the method of close inbreeding, the Booths (Thomas,John and Richard), Thomas Bates and Amos Cruikshank in turn brednew and different types of Shorthorn cattle,

Breeding to type was much assisted by the show-yards which soon carneto be formed. The first of these shows was that of the Smithfield Club,founded in 1798. This did much to develop early maturity to the greatadvantage ofthe feeder and the butcher. The Royal Agricultural Society'sShows were founded for breeding stock and this was followed by numerouscounty and other local shows, and at all of these, as at the SrnithfieldShow, prizes, medals or other awards were made for the best animals,and this practice still continues.

To assist in improvement, production and progeny tests have since beeninstituted. The Smithfield Club has kept records of carease tests sincer895, the classes being judged by butchers to meet the changing tastes ofthe public for quality in meato In a similar way the National Pig Breeders'Association has carried out carease tests for bacon and pork. For dairycattle, rnilking trials have been held at the London Dairy Show since 1876,as wcll as the Royal Agricultural Society's Show. SimilarIy, milk yieldswere recorded for cows, the Ayrshire andJersey societies being among thefirst to do this, and in order to get a uniforrn practice throughout Englandand Wales, the Board of Agriculture orgaruzed a regular system; registerswere compiled of cows with consistent high production, butter-fat testswere made, and other points such as quantity, quality and colour of butterwere recorded.

The 'progeny testing' of sires and darns was subsequently introducedinto the show-yards at the Royal and Dairy Shows and awards given forthe collected progeny of an individual bull; furthermore, registers of meritfor male anirnals which sired cows of outstanding merit have been published by various societies. The systcm took origin in the practice of lettingout a young bull or ram to other breeders to ascertain the qual ity of theprogeny before using thern upon specially selected females.


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4 The Application oj Science to Animal BreedingThe publication of flock-books for sheep and stud-books for horses of

different breeds very soon followed the institution of herd-books for cattle,and the tests adopted have been in general very similar. For racehorses, asalready mentioned, there was the additional performance test of the racecourse, and Allison has remarked that the 'mercanti le test' is the safestguide to the successful breeding of the British thoroughbred. The importance of progeny tests has also been appreciated by horse-breeders, andthe 'figure-system' of Bruce Lowe and Allison was an attempt to applythis test in a particular manner. It was claimed that in order to producethoroughbred horses of merit it was necessary for the parents to havenot only 'running blood' but also 'sire blood' (which was supposed toperpetuare the power of getting winners}, and figures were assigned tothe various farnilies denoting, in order of merit , the numbers of winnerswithin these families. In brief, without a sufficiency of 'sire blood'in the pedigree of a horse, the chance of its producing winners wassmall.

In all the work briefiy dcscribed aboye, highly successfuI though it was,there existed little, if any, consciously applied science, and this is thejustification of Bateson's remark, quoted at the opening of this account ofthe history of scientific breeding. It is now undcniable that the breedingof livestock was hampercd by prejudice as we11 as ignorance such as couldonly be overcome by exact scientific tests and the application of acquiredknowledge.

Even at the beginning ofthe present century the physiology of'reproduction was still in its infancy, and such observations and experiments as hadbeen made were most uncorrelated and little regard was paid to them.Nevertheless, the importance of precise scientific method was envisagedby a few, and it was these men who started to make experiments and toconduct inquiries on their own with little or no financiaI support. Theinfluence of Darwin and the other great biologists of the Iatter half of thenineteenth century upon these men was very apparent, while the generalacceptance of the doctrine of organic evolution and the theory of naturalselection as a factor in the production of new species brought about in alleducated men a transformation of outlook which extended to breeders ofanimals.


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Francis Galton 5FRANC I S GALTON

Sir Francis Galton (1822-1911), a cousin ofDarwin, founded in the lastyears ofthe nineteenth century the biometrical study ofheredity. Althoughhe was rnainly interested in the study of human heredity, his law ofancestral .in her itance-i-tha t the two imme dia te pa re nts contributedbetween them one-half of the effective heritage, the grand-parents enefourth, and so o n - h a d a large influence on stock-breeding. I t was on thisidea that the Breed Societies constructed their extended pedigree system.It is not without significance that the characters, such as stature, whichGalton investigated were those that also interested the stock-breeder. Inthis method of research he was followed at a later date by Karl Pearson,who, among other things, showed that the intensity of inheritance asmeasured mathematically varied in different parts of the body; thesignificance of this was not recognized until afterwards, when it wasrealized that sorne parts are more susceptible to the nutritional envirenment than are others.

J. C. EWARTAmong other matters o f both scientific an d practical importance and

upon which animal breeders were apt to maintain views since proved tobe partIy or entire1y wrong, were the questions relating to inbreeding,prepotency, th e inheritance of acquired characters, telegony (and, in itscumulative form, saturation), a nd m at er na l impressions. One of the firstto undertake extensive work upon these matters was Cossar Ewart (18511933), Regius Professor ofNatural History in the University ofEdinburgh.About the year 1895 he acquired land at Penycuik, Midlothian, an d herehe established a private experimental farm for animal breeding an d begana long series of investigations in Genetics, in which he was a pioneer.Since the time of Darwin there was no ene, at any rate in Britain, whohad devoted himself to this kind of work, an d it was both arduous andexpensve an d requiring much patience and foresight. Sorne of the moreimportant work was done before the rediscovery o f Mendel's Iaws ofheredity, referred to below, but by adopting such methods as were knownto him, Ewart successfully conducted a number of investigations uponprepotency, cross-breeding, inbreeding and reversin, as well as upon


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6 The Applicaiion 01Science to Animal Breedingtciegon y and similar real or supposed phenomena among horses ofvariousbr ceds and other domestic animals, He fully realized the potentialeconomic importance o f such work, and was not slow to ernphasze thedesirability of applying scientific methods to the study of reproductionin thc interests of the breeding industry.

Ewart's paper on 'A Critical Period in the Development of the Horse'(1897), in which he showed the reason wh y mares tend to slip foal at orabout the sixth or seventh week of pregnancy (when the type of placentation or mode of attachment of the embryo to the mother is changing fromthe primitive yolk-sac or marsupial type to the aIlantoic type whichcharacterizes most of the mammalia), an d pointcd out the need for extravigilance on the part of the stud groom at this time, supplies an exampleof a physiological discovery o f practical significance, an d Allison, theSpecial Commissioner of the Sportsman newspaper, emphasized i15 importance in the pages of that journal.

Ewart's most famous experimenta were probably those relating to telegony or the theory, widely entertained both by me n of sciencc and bypractical breeders, that a previous sire may so 'infect' the dam served byhi m as to impress certain of his characters upon he r subsequent ofspringby other sires. The theory of saturation was an extension of that oftelegony , and postulated that a dam by being servcd over a number ofyears by a particular male had his characters so impressed upon he rthat her offspring after successive pregnancies became more and more toresemble the sire. Darwin himself appeared to accept the theory of telegony, an d Allison, in his book on The British Thoroughbred Horse, statedthat the truth of telegony was established fact and that it only rcmainedfor scientific men to supply the physiological explanation. There can beno doubt that nearly all breeders took the same view, which is even no wstiIl held by sorne.

The classical case ofthe supposed phenomenon, which is cited at lengthby Darwin, was that of Lord Mortori's Arab mareo This m a r ~ , after firstbeing served by a quagga and producing a striped hybrid foal, afterwardsgave birth to an Arab foal as a result of mating with Sir Gore Ouseley'sArab staIlion. This foal, which is figured by Darwin, had striped markingsthat were said to resemble those of the quagga with which the mare had


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EVOLUTlON IN THE SHORTHORN BREEDT op : Cow o 1840 by Reforma , Dam b)' Raby, Grandam b)' Sir Oliva , Centre: DniryShorthorn Coto o 1938, Knells Elliot Fernleo f 2/1d. B ottom: Beef Shorthorn COIV rif1939, Scotston Laueuder Lass


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J. C. Ewart 7first mated. Ewart repeated the experiment, but the quagga as a specieshaving become extinct, he employed a Burchell's zebra stallion, and thisserved mares of several different brceds, and got str iped hybrid foals.The mares were afterwards put to stallions of their own breed, but theresulting 'subsequent foals' never showed any sign of having been affectedby the pr vious zebra sire, Ewart carried out other telegony experimentswith various species of animals and they were all uniformly negative asregards any evidence of the occurrence of the phenornenon. Accounts ofthis work, together with the results of other breeding experiments, aregiven by Ewart in his book on The Penycuik Experiments (1899), in hispresidential address to the Zoology Section of the British Association in1903, and in numerous papers contributed to scientific and agriculturaljournals.

In 1913 the University of Edinburgh rented a farm at Fairslacks,Midlothian, and here Ewart kept a considerable number of sheep ofdifferent breeds and started experiments designed to improve the fleece,This work brought him into contact with the woollen industries of GreatBritain and they realized the importance of the work, In 1923 he wentto Australia at the invitation of the New South Wales Govcrnment andvisited many important and some very outIying sheep stations. He thenproceeded to New Zealand and conducted similar work there. There canbe no doubt that these investigations lcd to the fur ther recognition ofthe economic importance of scientific breeding, In 1924 the WorshipfulCompany of Woolmen in London struck a gold medal, which theypresented to Ewart in recognition of what he had done.

W AL T E R H EA P EIn the meanwhile Walter Heape (1855-1929), whose name is mentioned

at the beginning of this s h o ~ t history, had formulated and conducteda scheme of inquiry into certain other matters connectcd with sheep,and more particularly those dealing with feeundity. The inquiry wasconducted under the auspices of the Evolution Committcc of the RoyalSociety, ofwhich committee Heape was an original member (1896). Theinvestigation was carried out with the co-operation of the Royal Agricultural Society, and a full report was published in 1899. It dealt chiefly


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8 Tlu Application 01Science to Animal Breedingwith the incidence of abortion an d barrenness in the different Englishbreeds, and the causes were shown to be different, depending b oth up onbreeding and feeding, and to vary with local conditions. The generalfertility of the breeds was also compared and many useful suggestions ofgenetical value to farrners were put forward. At a later date a somewhatsimilar inquiry was carricd out in Scotland by the Highland an d Agricultural Society (MarshalI, 1908). Among thc prac tical conclusions whichresulted from these studies was one on the effects of 'flushing' shcep; thatis, supplying thern with extra corn, cake or turnips or p utti ng th em up onsuperior pasture or a good new ley a t the approach of the tupping orbreeding season. Sheep brcedcrs had al ready found that these practicesgenerally increased the fecundity of the ewes, but the matter was no tclinched unti l it was shown that under th e conditions of flushing th e eggcontaining follicles in the ovaries ripened more rapidly, an d that at th eperiods of oestrus or heat two or more eggs would often be dischargedrather than one, the final result being an increase in the number of lambsborn. Another matter of interest concerned the inheritance of fertility.The evidence collected showed that rarns which were born as twins andno t singles could tra nsmit th e fertility of their dams to th e nex t generationof ewes, and consequently that the practice ofbreeding from singles ratherthan twins was one to be deprecated, notwithstanding that the rams whichwere single lambs were often better developed owing to their havingobtained more nourishment from their mothers in th e early days of theirlives,

Heape also published an important papel ' on artificial insemination(1897). This practicc, although there is evidence that i t ma y have beenknown to the Arabs, was first elearly demonstrated by thc Italian biologistSpallanzani (1784) in the successful insemination of a bitch. But it wasnot takcn much notice of until Heape called attention to it by publishingthe experiments by Millais, in which by this method he effected crossesbetween Blood-hounds and Basset-hounds (two breeds differing considerably in size). Heape also emphasized its probable importance to horsebreeders, qu oting th e reports of t he R oy al Commission on horse-breedingin which it was shown that the percentage of sterility in thoroughbredsin any one year might be as high as 40 per cent. One of the earliest


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Walter Heape 9successes in inseminating horses was when the thoroughbred mare Sandi-way was successfully impregriated by injecting semen obtained frorn thestallion Trenton and afterwards produced a first-class foal named Sand-flake. The more recent deveIopments and applications adopted in thepractice of artificial insemination are referred to below.

Heape's best known and probably his most important work was hismemoir on The Sexual Season oj Mammals (1900), in which he gave acomparative account of the oestruaI or breeding cycles in all the differentanimals for which any data existed. This was soon followed by fuller,more detailed accounts by others on the oestrual cycles of the sheep, thedog, the ferret, and the rabbit, and in recent years similar studies havebeen made for a large number of other animals.

Heape's book on The Breeding Industry has been mentioned aboye in theopening paragraph. In this book, which contains much statistical informa-tion, he stressed the great economic importance of animal breeding inGreat Britain and the heavy losses which were annually incurred throughfailure to apply scientific methods to animal production for commercialpurposes. In particular he stressed the importance of breeders keepingrecords so that their experiences should not be lost but be made availableto the community.

GENET I C S IN CAM BR IDGE -W I L L IAM BATESONAnother Cambridge man who played an important part in promoting

and taking part in the study ofbreeding was Wilam Bateson (1861- 1926),whose first book entit1ed Materials for the Study oj Variation, by its insistenceupon the phenomenon of a discontinuity in organisms, gave a fresh orienta-tion to the way in which problems of reproduction and evolution wereregarded. Then in 1910, with the disinterment ofGregor Mendel's Versucheber Pflaneen-Hybriden (originally published in 1865), there appeared theclue for which Bateson had been seeking, and he and his co-workers inCambridge made much of it in ' working out the inheritance of manykinds of animals and plants. In the mean time, Bateson brought out inCambridge an English edition of Mendel's work in the book entit ledMendel's Principies qfHeredity (lg0g).

The original experimenta of Mendel, as is well known, were upon


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10 The Application 01Science lo Animal Breedinghybridization in peas, the two parent varieties initially seIected differingfrom onc another in ane particular character. The hybrids produced incrossing were all similar superficially and resembled one of the parentsin the character in question, which was therefore called the dominantcharacter , the other character being known as recessioe. When the hybridswere crossed among thernse lves, approxirnately one-half of the offspringwere found te> be identical with the parent hybrids (dominant hybrids),one-quarter also superficially resernbled one of the original varieties (thegraudparent with the dominant character), while the remaining quarterwere like the other pure varicty (the grandparent with the recessivecharacter ). Thus the pure dorninants and the dominant hybrids resembledone another ourwardly, bu! they differed in their capacity to transmitthc charar teri stic in question, since the pure dominants alone invariablybree! true. Th e reccssives also always bred true. Mendel drcw the conclusion that in the hybrid the gametes (both sperrnatozoa and ova) wereof two kinds in respect of the characters they carried, or gave rise to,and they were respectively identical with the two kinds represented bythe garneres of the original pure varieties. The differentiation of gametescarrying diflercnt characters is the essential principIe in Mendel's theory,the existence of dorninant and recessive characters, though often observable, being by no means universal.Thc Mendelian coneeption of gametic differentiation is the principIeunderlying all thc later work of Bateson and his pupils. Among the earlierinvestigations in Cambridge was that of himself and R. C. Punnett, whoafterwards succeeded him, upon the blue AndaJusian fowJ. Keepersof ths breed had always recognised the practical impossibility of obtaining a pure strain. However carefully the birds were sclected theyinvariably prcduced two sorts of 'wasters', sorne being pure bIack andsorne white with irregular black marks or splashes. Bateson and Punnc ttwcre the first to supply the explanation. They found that in breeding froma large number 01 blue Andalusan fowls, on an average half of the offspring were blue like the parents, a quarter werc black and a quarterwere splashed-white. They conscquently drew the conc1usion that themechanism of inheritance in the Andalusian fowl was comparable to whatMendel supposed to exist in his hybrid peas. The gametes of the brced,


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Genetics in Cambridge-s-William Bateson 11instead ofbeing a1l similar and carrying the blue character (as one wouldhave supposed on Weismann's or any of the old cr theories of heredity)were of two differcnt kinds, those of the one kind carrying the blackcharacter and those of the other being bearers of the splashed-white.Such gametes, uniting by chance when the fowls mated together, gaverise to three kinds of offspring, (me black-white (becoming blue actuallylike the parents), one black-black, and one white-white, these appearing(on the average) in the proportion of 2 : 1 : 1 , according to the law ofprobability. In this particular case of Mendelian inheritance, neither ofthe two altcrnative parent characters (black and splashed-white) wasdominant and neither recessive.

I t will be seen from the aboye that the Mendelian conception ofdominance gives a precise significance to the older iclea of prepotencyon which Ewart had been working in Eclinburgh. One of the earliestworkers to apply the Mendelian laws to farrn animals was]ames Wil son ofDublin, who used them to explain the evolution of thc British breeds of cattleand to elucidate the problem of 'bulldog' calves in the Dexter breed ofcattle, a matter which was later investigated indetail by CrewatEdinburgh.Among other experiments carried on by the Cambridge School of

Genetics were those of T. B. Wood on the inhcritance of horns and faceeolour in sheep (Igog). By crossing Suffolk sheep with Dorset Horns,Wood was able to superirnpose the complete hornlessness of the formerbreed upon the white faces of the latter, but in sorne of the hornless sheepthe transmission was not 'purc' since certain individuals grew very shorthorns or scurs, The experimcnts as a whole were, however, further evidence that the principies of Mcndelian inheritance could be applied todomestic animals.

Furthermore, in Iater experiments in which Merino rarns were crossedwith Shropshire ewes it was shown that sorne of the more importantcharacteristics of the body 01 ' carease (that is to say, the 'rnut ton points')rmght be transmitted to the third generation so as to appear in newcombinaticns in the cross-bred sheep. Thus, taking the four points, 'overthe shoulder', 'behind the shoulder', 'top of leg', and 'loin', which arewidely different in Merinos and Shropshires (being 'bad' in the formerand 'good' in the latter in regard to mutton production), segregation


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12 The Application ofScience to AnimalBreedingappeared very clearly in animals of both the second and third generation,the points being rcproduced in all possible combinations among the crossbred sheep. This case of apparent Mende1ian transmission was all themore rernarkable in that the characters were not superficial, but deepseated and re1atcd to bodily conforrnation, each of them depending on anumbcr of anatornical factors. It could not be said, however, that all thecharacters were inherited 'pur', and in some animals they were definite1ycomposite, being different frorn those of both the parent breeds (K. J. J.Mackenzie and F. H. A. Marshall, 1917)." Throughout the period there was no proper accommodation for keepinganimals [01' experiments in Genetics, and Ior the purposes of the investigations just referred to the premises used were Bateson's private gardenat Grantchester, the University Farrn, and Wood's private farm inNorfolk.In 1g08 the University of Cambridge created for Bateson a chair in

Biology, but he he1d this only until the end of IgOg, for in 1910 he movedto Mcrton, Surrey, in arder to take up the directorship of the John InnesHorticultural Institution, where his work on Mendelian inheritancerelated exclusively to plants. Thc animal work at Cambridge was, howevcr, carried on by R. C. Punnett, who succeeded Bateson in thc chairofBiology. In 1912 a new chair in Genetics in Cambridge was insttutedand to this Punnett was appointed, arrd a School ofGenetics with Government support was founded with adequate buldings and accommodation[al' thc srnaller animals, and much valuable work on poultry and rabbitshas been "done, notably the work on the inheritance of body sizc carriedout in conjunction with P. G. Bailey.Together with M. Pease, Punnett produced a sex-linked breed of

poultry which would breed true-the Cambar, the cocks of which athatching had a much paler clown colour than the pullets. This was madeby combining the barred pattern of the Plymouth Rock with that of theCampine. From this breed many new sex-linked varieties of the commonbreeds of poultry are now being produced. This latter work was carriedout by Pease at the Animal Research Station-the fie1d station of theAnimal Nutrition Institute ofthe School of Agriculture. The ficld station,consisting of laboratories, animal houses and sorne eighteen acres of land


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Weight-gr-s .~ ' - - /9 5

Foctal ,ltrojd])' in Pigs ( (rom Hammond, r.940 )The foeiusesJ iom a rol!' sholcillg their ]eloiioe positiouin the ulcrus (Inri thc weighl of each f oetus. Al thoug]pregll(Ul(Y is not f m aduanced, 2 f J ] ~ Y u the foe iuses

halle degtlleraler/ and oihers me about 11) die


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Shetland-Shire Crosses ifrom [,jal/U/l & Hammond, 1938 )Thc maternal effcct on the sire of the foa! in reciproca! crosses betuieen the large Shire liorse ami small Shetlaudpon'." all to the samc sra/e. Top line-s-Parents: Shire stallionX Shetland mate, and Slnre mureX Shetlaiulstallion. Middle line: Their respectioefoals al birth. Bouom tine: Thefo als al one montlt old


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Genetics in Cambridge-William Bateson 13situated on the University Farm, was built with the assistance of theEmpire Marketing Board in 1934. Pease, in conjunction with the PoultryRcscarch Station at Reaseheath, Cheshire, also developed inbred lines ofWhite Leghorns, which are proving themselves useful for mating to otherstrains to 'produce good laying birds.

G E N E T IC s 1 N E D 1 N B U R G H - F. A. E. e R E WIn thc meanwhile, great progress was made in developing the scientific

study of animal breeding in Scotland. Shortly before the war of 1914-18,and chicfly through Ewart's influence, the Board of Agriculture forScotland appointed a special committee to deal with this matter. Afterbeing for some years in abeyance, this committee in 1919 beca me activeand appointed F. A. E. Crew director of research, and this position heretained until 1944-, but he was necessarily absent on national service from1939 onwards. As a result ofliberal benefactions, the scheme was greatlyenlarged, and a new and fiourishing Department of Genetics with aconsiderable staff ofworkers was formed in the University of Edinburgh.A chair was founded in 1928 and Crew became the first Buchanan Professor of Animal Genctics, only resigning to take up a new professorshipin the university in 194+ During the period of his directorship Crewpublished several books (Animal Genetics, The Genetics oJ Sexuality, etc.) andhe and his staff bctwcen thcm produced a very large number of papersdealing with experimental work on animal breeding. Among these maybe mentioned the work of Finlay, who organized a Cattle Breeding Confercnce at Edinburgh in 1924, of Roberts on the inheritance of colourand other characteristics in sheep, of Calder on the coefficient of inbreeding in herd-books, and ofBuchanan Smith and Donald on studies ofherd-books. A. Greenwood, who started work at Edinburgh on stuclies ofthe physiology ofdevelopment in the fowl, began in 1931 a genetic analysisof the factors affecting egg production in a strain of Brown Leghorns. Heseparated out, by selection and inbreccling, lines which showed differentcharacters, such as intensity of production, large and small egg size, largeand small body wcight, etc.-work preliminary to combining the desirablecharacters in one strain.


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14 The Application 01Science to Animal BreedingResearch students from various universities throughout the world took

up temporary residence in Edinburgh and worked in the Genetics depart-ment, availing thernselves of the new buildings and accommodation atNether Liberton on the outskirts of Edinburgh, and these contributed tothe output of work, which grew in volume until about the time of theout break ofwar. The Imperial Bureau of Animal Genetics was establishedat Edinburgh in 1932 to collect and disseminate the knowledge on AnimalBreeding; the late Deputy Director, ] . E. Niehols , has also published abook on Lioestock Improoement, which describes the relation of heredi ty toenvironment.

AN IMAL PHYS IOLOGY IN CAMBR I DG EThe work done in Cambridge, described or alluded to aboye, was

almost exclusively carried out in conneetion with the Zoological Depart-ment of the University or, as has been shown, in the newly created Sehoolof Geneties; it deaIt mainly with the problems of heredity and variation,the study of whieh had becomc a new braneh of biologieal science. Butin 1908 a series ofinvestigations was started in conneetion with the rapidlyexpanding Sehool of Agriculture in Cambridge, and it remains to givesorne account ofthe historyof this movement which was more particularlyconcerned with physiological research into the functions of the repro-ductive organs and its practical application to the control of animalbreeding. Heape had left Cambridge before 1908, but his influence stillpersisted, and the inception of the scheme for research on the functions ofthe generative organs and the fertility of the domestic animals and othercognate problerns must be traced to his writings .In 1gog Professor J. N. Langley, realizing that ordinary laboratory

accornmodation was quite insufficient, formed a committee, of which hebecame chairman, to deal with the acquirement of land and buildingswhich could be used for researches on the animals of the farm. On thiscommittee the Schools of Pathology, Parasitology, Biochernistry, andAgriculture, besides Physiology, were represented, and it was agreed thatthese departments should act jointly in the matter. As a result land waseventually acquired and contributions from each of the departmentsagrced upon, and in this way the Field Laboratories of the University of


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Animal Physiologs in Camb ridge 15Cambridge were started. In 1919, after the terminati on of the Germanwar, therc was foundcd in association with thc School of Agriculture anInstitu te of Animal Nutrition , and this contained a sub-depar tment todeal wi th reproduction and allied subje cts in farm animals, and a directorof this sub-departrncnt (F. H. A. Ma rshall) was ap pointed. The agricultural section of the Field Laboratories then became sepa ra ted offfromthe other sections, but the work on the physiology of animals was stillcontinued for sorne yea rs at the old headquarters on thc road leading outof Cambridge towards Ely. In rgQ3,wi th the form ation ofa new UniversityDepartment of Animal Pathology, the whole of this land carn e to formpar t of the new department, which had its own professor ; and those whocontinued to work there were exclusively occupied with the study ofanimal diseases. In the mcan tirne, the work on physiology was transferredto Huntingdon Road in proximity to th e Universi ty Farrn , and it is stillbeing continued in enlarged premises, These deveIopments occurred inresponse to an increasing realizaticn of the practical importance of suchstudies to the farming community and to th e country and ernpire. TheEmpire Marketing Board gave th e gr eater par t of the finan cial suppor t,while the Rockefeller Trust, by thei r generosity in providi ng endowmentsfor teaching, assisted indirectly by relieving the demands upon oth erfunds which were drawn upon to support research. The DevelopmentCommission and the Ministry of Agriculture provided the working expenses(and later, aftcr its formation) with guidance from the Agricultura!Rcsearch Coun cil. In the meantime, thc original buildings of th e Schoolof Agriculture were more than dou bled in size.

Mu ch work on physiology was also done in the bu ildin gs of the Schoolof AgricuIture itself where smaller animals could be kept Ior purposes ofexperiment, while sorne of the animals on the University Farrn wercutilized from the first. Moreover, in conneetion with the sa rne work, visitswere paid to other farms for the purpose of an imal study as wcll as tobacon factories at Calne and Du nmow, where special investigations werecarried out in association with the work in Camb ridge.

The earlier work on thc ovary as an organ of internal secretion and itsinfiuence on the periodicity of the oestrual al' sexua l cycle was carried outin Edinburgh, and evidence was adduced that the sexual glands controlled


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16 The Application 01Science to Animal Breedingthe changes which occurred in the other organs of the body in associationwith the processes of breedng. I t had formerly bcen supposed that someof the se changes might take place in the absence of the essential organsof reproduction, but this was definitely found to be crroneous. Severalworkers confirmcd the hypothesis ofBorn and Fraenkel (in Germany) thata structure called the corpus Iuteum, which is formed in the ovary after therupture of the follicle and the discharge of the egg, played an importantpart in prcgnancy and was a factor in the development of the udder. Thiswork was extended in Cambridge, and complete studies of the physiologyof the oestrual cyc1e and pregnancy in various animals were carried outthere (see Marshall, 1922; Marshall and Halnan, 1935; Harnmond , 19'27).

Among other matters of interest it was conclusively proved that byspaying (ovariotomy), the removal of the ovaries 'Nassufficient to preventthe recurrence of heat 01 ' cestrus, the extirpation of the uterus 01' 'bed'being unnecessary, and that spayed sows tended to fatten faster and betterthan 'open' 01' unspayed ones. Moreover, the mammary tissue in spayedpigs did not develop, and consequently the black pigment in the neighbourhood of the teats in black 01' black and white breeds 01' pigs was notforrned, since it is normalIy confined to the mammary tissue. In this waythe condition of the belly-piece known as 'seedy-cut', which is due tosuch pigment, could be avoided, 'seedy-cut' being deprccated by baconmanufacturers as it disfigures the meato K. J. J. Mackenzie was one ofthose who took a leading part in these investigations,Another of the earliest studies in Cambridge was one on fatness as the

cause of sterility in domestic animals. I t was known that very fat animalsdid not come in season in a marked way and that their heat periods wereoften irregular, and that the animals might even fail to breed altogether.Nevcrtheless, the value offat animals was such that it induced the farrnerto fatten them to so great an extent that they might be rendered ternporarily 01 ' even permanently sterile. The Cambridge inquiries dealt withthe physiological condition of the breeding organs of such. animals andrevealed the reasons why they were unabl'e to brecd, thus confirmingthe experiences of those practical farmers who deprccated the practice ofundue fattening. In general, it was shown that whcrcas the supply ofgoodfood raises the nutrition and increases the bodily vigour and fertility, over-


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Animal Physiology in Cambridge r 7feeding and laek of exercise lead to exeessive storage of fat and reductionof vigour and fertility (see Marshall and Hammond, 194-5).An investigation was also condueted upon low fertility in pgs which

normally have large litters. It was shown that reduced fertility in many ofthe pigs was caused by the atrophy of the foetuses during pregnancy andgenerally in early prcgnancy (Hammond, 1914). The results "vere cornpared with those found in sorne str ains of rabbits, in which the foetalatrophy was found to be a reeessive genetie character (Hammond, 1928).Among the more irnportant work done during the succeeding decade

was that of Professor T. H. Bissonnette, who carne from U.S.A. and proceeded to work on the part played by light in bringing animals into abrecding condition. His experiments showed that ferr ets could be broughton heat and made to breed by subjeeting them to artifieiallight or ordinaryelcctrieal illumination in the winter, when the anirnals are norrnally in thenon-breeding condition. His rnethod was to supply the ferrets with theillumination at the end of the day, thus extending the period of light to alcngth comparable to that which they normaUy experience at the comingof spring. A large body of experimental and observational evidence hassincc shown that a very considerable number of other vertebra te animalsrcact similarly to light. The practice adopted by the poultry industry ofsubjeeting hens to artificial illumination in order to promete egg-laying isprobably an applieation of the same principie. Later experiments showedthat non-luminous ultra-violet irradiation applied to ferrets may be evenmore effective than light. .Further, fundamental investigaton of the factors which control fertiliry,

so important to the whole bre eding industry, was now actively pursucd.It was shown that the number of eggs ripened by an animal depended onsorne substanee cireulating in the blood and not on the structure of theovary itself, for when one ovary was removed the same number of eggswere shed as in an animal with two ovaries (Asdell, 1924-). This substancewas later found by workers in U.S.A. and Germany to be a secretion fromthe anterior pituitary gland, and a substance with the same effect could beobtained from the blood serum of pregnant mares between the forty-fifthand ninetieth days ofpregnancy. Experiments still in progress have shownthat these substances can be used, by injection a few days before service, to


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18 The Application 01Science lo Animal Breedingproduce twins or triplets (according to the amount injected) in beef cattle(Hammond, Jm., and Bhattacharya, 1944). These substanees are abobeing used to make sheep breed out of season and so breed three erops oflarnbs in two years, as well as to make goa ts kid in the autumn monthsand so add to the supplies of'winter rnilk.

The causes of sterility among pedigrcc stock are many. In ord cr toinvestigate these in thoroughbred horses, an exper imental stud was startedin 1935 at Newrnarket with the assistance of the Thoroughbred Brecders' .Association and the Agricultural Resea 'eh Council with funds dcrivedfrorn th e Bctting Control Board. Mar es which had been sterile for threeyca rs werc taken in , studied by F. T. Day, F.R.C.V.S.,. and when gotin foal were returned to their owners, This work had to be discontinu edat the outbreak of war in 1939, but not befare several of th e main causesof sterility had been determ ined and methods for che early diagnosis ofpregnancy developed. The Iatter proved most uscful during the war whensupp lics of pregnan t mare serum hormone were obtained from wild Welshmountain ponies.In 1922 a section of the Insti tute was devoted to th e study of malc

fertility and sterility, The earlier work of Heape (see aboye) on art ificialinsemination was extended particularly with respect to the problern ofpreserving th e life of th e spe rm outside the body by con trol of tempera turc- t h e optimum being 4:oF .-and th e respiratory proccsses (vValton,1930) . Successful long-d istance transport of semen was achieved in 1927,ra bbit spe rm being sent between Cambrid ge and Edinburgh by post.La ter, when methods developed in U.S.S .R. for collecting semen fromthe larger farm animals became available, long-distance transport of ramsemen to Poland (Walton and Prawochenski, 1936) and bull semen toHolland (Edwards, Walton and Sieb enga, 1937) was achieved in cooperation with scien tists in thosc coun tries. Ano ther aspect of th is workwas in its applica tion to the mass production of th e best genetic typ esamong farm animals , particularly among dairy cattle in which there is nomeans of judging the genetic value of the bull unt il his first daughterscome into milk, at whi ch time he is at least six yea rs old . Calves Irom suchbulls preven for high milk production can now be produced at the rate ofabout a thousand a year, in place of the thirty to fifty by natural rnatings.


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Animal Physiolog in Cambridge 19Earlier statistical studies of the wastage among dairy cows, by H. G.Sanders in Cambridge and by N. C. Wright and others in different arcas,showed sorne 20 per cen t were cu lled because of low yields, while furthcrstudies by J. Edwards showed how thi s was due lai gely to the unknowngenet ic qu alities for milk production of the bulls uscd in the industry. T heapp lica tion of artificial insemination from proven hulls should thereforehave considerab le economic advantages.

The first steps towards a similar extension of the reproductive powers ofgood genetic stock on the female side were begun in 1929 by G. Pincus, avisiting National R escarch Council Fellow from H arvard University, who,fol1owing work initiated by Heape, cultivated th c fertilized eggs of th erabbit outside the body and later successfully transplanted thcm intoother does, By the use of anterior pituitary hormones (see aboye) he wasable to ob tain up to fifty or more fertilized cggs a t one time for th is purpose.These experiments have yet to be extended to farm animals, in which thepossibilities are great.

In breeding for milk, one of the difficul ties met with in th e sclection ofth e dairy cow by milk records is in determining how far the environrnentalconditions affect the yield given . A statistical investigat ion of the factorsaffecting milk yields was published by H . G. Sanders in 1928, and thi senabled 'correction factors' for age, dry period, service period, etc., to bemade. This investigation led to a study of the way in which the ud dergrows to produce milk. Observations on heifers in calf for th e first timeshowcd that a sudden in crease in th e growth of the milk-secreting tissuesof the udder occurred at th e twentieth wee k (Ham mond , 1927). Lat crexperirnen ts by Wallace showed that th is growth could be augmentedconsiderably by a high level of feeding in the la ter stages of pregnancy.It was found, too, th at the st imulus for growth carne from chernical substances--oestrogens- produced in th e pl acenta and circulating in theblood. Synthetical1y produced ch cm ical substances wi th an actiou similarto the ocstrogens were produced by Prof. E. C. Dodds , Middlesex H ospital,London. J. H ammond, J nr., and F. T. Day, using these sub stances by themethod of tablet implantations, developed in 1\. S. Parkes's laboratory atthe Na tional M edical Research Institute, Hampsteacl, wer e able to obtaingrowth of the udder and milk yields of up to 30 lb . p er day witb a normal


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20 The Application 01Science to Animal Breedinglactation period in heifers which had never been pregnant, Experimentaon similar lines in cattle and goats were also conducted at the NationalInstitute for Rcsearch in Dairying at Reading by S. J. FoIley an d hisco-workers. These experiments indicated some of the basic ph ysiologicaIfactors which have to be taken into account when breeding for such acomplicated character as milk production.

The size and vigour of the young at birth p lay a material part in thesurvival rate of all animals an d especially of sheep, in which parturitionfrequently occurs under exposcd conditions. Studies on the effects of l.high planc of nutrition in the later stages 01' pregnancy in increasing thebirth weight and vigour ofthe lamb by Hammond (1932), Verges (1939 b)and Wallace (1944) suggested a remedy for the large losses which occurat or shortly after lambing time owing to the birth ofweak lambs. Similarresults were also obtained by W. Thomson an d A. H. H. Fraser in experiments at the Rowett Research Institutc, Aberdeen.

Early experiments with rabbits had shown that the weight 01' theindividual young decreased as the number in the litter rose, and thisraised the problem of how far the nutritional environment of the mothercould affect th e ultimate size an d development of the young. Reciprocalcrosses, by means of artificial insernination, were made between the largesthorse (Shirc) and small est pony (Shetland), an d it was found that therewas a maternal, in addition to a genetic, influence of the mother not onlyon the birth weight (see illustration) but also on the ultimate size whichcrosses attained (Walton a nd H am mo nd , 1938).

The experirnents made by Mackenzie an d MarshaIl (1917) on theinheritance of mutton qualities in crosses between Merino and Shropshrcsheep had shown the necessity for a more accurate definition of mea tqualities in animals before much progress could be made in brccding forspecific meat qu alities. This led to a study of the growth and deveIopmentof the mutton qualitics in the shcep by P. G. Bailey, a geneticist, unfortunately killed in the war of 1914-18; A. B. AppIeton, a comparativeanatomist from the Cambridge University Departmen t of Anatomy; and] . Hammond, a physi ologist from the Insti tute of Animal Nutri tion; an dthe results, published as a book (Hammond, 1932), present an accountof the scientific principIes which form the basis of meat production in the


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Crowlh Changas in the Pig (1 ,011 Hauunond, '940 )Each animal ir icduced lo the same headsirr. il s IlI/ imbrooed breed like lheMiddfe Wltite grnws up, the fJ fofJO r l ioTl 01 loin lo head and nrrl: increasesgreaI0'; but an unimprooed ) ' P e JUe/1 as ihe Wild B OIl /" g rolt'J up uiithoutmucli cliange in bod)' propor tions, 'Top: Fceiu, o 2 months. 211d fine:Middle WhiteJ ioeek old, Jj/b . 3 rd tille: M iddle IVhite-Ij ioeekssu. JOO lb. Bottom: Wild Bom- adlllt , alioul300 lb.


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Animal Physiology in Cambridge 21animal. This was followed by analytical studies of the meat qualities ofdiffercnt breeds of cattle, pigs and sheep, made by visiting research workersfrom other countries (Hirzel, 1936; Hammond and Murray, 1937; Plsson,1939-40), and derived from carease tests at shows and selected animalsfrom brecders. Later, experiments on the effect of the nutritional leve!during the growth period in pigs (McMeekan, 1938) and in sheep (Verges ,1939 a) showed how important a high nutritional level is for the fullexpression of the genctic characters of the animal for meat purposes. AHthese results suggested the conclusion that, for meat purposes, thc nutri-tional environment in which selection of breeding stock 1S made is of thchighest importance for satisfactory progl'ess. 1t is only under such conditions of high nutrition that the full expression of the genctic characterscan occur and so progress can be made by selection. If the environrnentis not optimal for the development of the character for which sclcctionis being made, then the development of the character is limited by theenvironment and not by the genetic constitution (Hammond, 1940). Thusman has the power of directing the course of evolution, not only ofhis domes tic animals, but also of himself, by the environment, nutritionaland otherwse, which he himself creates for the rearing of thc nextgeneration.


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22 The Application ofScience lo Animal Breeding

BIBLIOGRAPHYFurther details concerning work quoted abooe can be obtained Jrom the Jollowingpublications, listed (excepting Jor the jirst reference under authors' names :

Animal Brccding Abstracts, 1933-47, Imperial Bureau oj Animal Breeding andGenetics, Edinburgh.AscleJI , S. A., 1924. Sorne effects of lateral ovariotomy in rabbits, BritishJournal oj Experimental Biology, I .Bateson, 'vV ., 18g4. Materials for the Study of Variation , London .-- , 1909. Mendel's Princ ipies oj Heredity, Cambridge.Bissonnette, T . H ., 1932. Modifi ca tions of mammalian sexu al cyeles.

Reacti ons of ferrets of both sexes to electric Iight added after dark inNovember and December. Proceedings oj lhe Royal Society (B iolagical), l IO.Calder , A ., 1927. The rol e of inbreeding in the Clydesdale breed of hors es.Proceedings of the Royal Society oj Edinburgh , 47.Crew, F. A. E. , 1925. Animal Genetics, Edinburgh .- - , Ig27. The Genet ics oj Sexuality in Animals, Cambridge.Darwin, C., 1859. The Origin oJ Species, London.-- , 1868. The Variation oJAnimals and Plants under Domesticaiion, London.Day, F. T ., 1940. Clinical and experimental observations on reproduction inthe mareoJournal oJ AgriculturalScience , 30.Donald, H . P ., 1940. Breeding pol icy in relation to performance testing in pigs.Empire J ournal oJ Experimental AgricuIture , 8.Edwards,]., 1932. The progeny test as a rnethod of evaluating the da iry sire .Journal ufAgricultural Science , 22 .--, Walton, A. , and Siebenga, F ., 1938. On cxehange ofbull semen betweenEngland and Holl and . J ournal oJ Agricultural Science, 28.Ewart, J- C. , 1897. A Cr ical Period in the Deoelopment oj the Horse, London.--, 1899 . Tlie Penycuik Experiments, London.Finlay, G. F., Ig25. Cattle Breeding, Edinburgh.Folley, S. j . , Seott Watson, B. M., and Bottomley, A. C., Ig4I. Studics onexperimental teat and marnmary development and laetation in the goal.

Journal Dairy Research, I2 .Galton, F ., I88 3. Inquiries into Human Faculty and its Deoelopment, London,Greenwood, A. W., 1935. Breeding for egg production. EmpireJ ournal01 Experi-mental Agriculture , 3 .Hammond ,j ., 1914. On sorne factors controlling fertility in domestic animals.Joumal oj Agricultura! Science , 6.- - , [927. Reproduction in the Cow, Cambridge.- - , Ig28 . Die Kontrolle der Fruchtbarkeit bei Tieren . Zchtungskunde, 3 .-- , 1932. Grounli and the Deoelopmeni oJMultan Q.ualities in the Sheep, Edinburgh.- - , 1940. Farm Animals: their Breeding, Growth and Inheritance, London.


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Bibliography 23Hammond , ] . , and Mur ra y, G. N. , 1937. The body proportions of differentbreeds of pigs. J ournal i f Agricultural Science, 27.Hammond , j . , Jnr ., an d Bhattacharya, P., 1944 . Control of ovulat ion in th ecow, J ournal o Agricultural Science, 34.- - , and Day, F. T. , 1944 . Oestrogen treatment of cattle: ind uced lactationand other effects. J ournal of Endocrinology , 4.Hcape, VV ., 1897. The artificial insemi nation of mammals . Proceedings of theRoyal Society, 6r .--, 1899. Abortion, barr enness and fertility in sheep. Journal i f theRoyal Agri.cultural Society, ID. .- - , 1900. The sexual season . Quarterly Journal ofMicroscopical Science, 44.-- , 1906 . The Breeding Industry, Cambridge.Hirzel, R ., 1939. Factors affecting quality in mutton and beef careases. Onderstepoort Journal uf Veterinary Science (South Africa ), 12 .Mackenzie, K.] . J., an d Marshall, F. H. A. , I g I 1[6. On ova riotomy in sows,with observations on the mammar y glands and internal gen ita l organs.Journal of Agricultural Science, 4-7.- - , 1917. T he inher itance ofmutton points in shcep. T ransactions o the Highland and Agricultural Socety o Scotland, 29.McMeckan , C . P. , 1940. Growth an d development of thc bacon pig, withspecial refcrence to ca rease qua lity, J ournal i f Agriculiural Science, 30.Marshall, F. H . A., 1905. Fcr tility in Scottish shecp. Transactions ofthe Highlandand Agricultural Society i f Scotland, 20 .- - , 1922. The Physiology ofReproduction (znd edition), London.- - a nd Halnan, E. T. , 1945. Physiology of Farm Animals (3rd edition), Cam-

br idge.- - an d Hammond,] . , [945. Fertility and animal breeding (6th edi tion),Bulletin 39. Min istry ufAgriculture and Fisheries.Nichols, J . E., [944. Liuestock lmprooemeni, Edinburgh.Plsson , H. , [939-40. Mea t qu alities in the sheep, wit h special refcrence toScottish brecds and erosses. J ournal ufAgricultural Science, 29 and 30.Pearson, K., 1900. The Grammar of Science , London.Pease, M. S., 1943. New Cambridge breeds of poultry. J oztrnal i f the Mini stryufAgriculture and Fisheries, 50.Pincus, G. , 1930. Observations on the living eggs of the rabbit, Proceedings ofthe Royal Society (Biological) , 107.Punnctt, R . C., 1905. Mendelism, London .- - and Bailey, P. G ., 1914. O n inheri tance of weight in poultry. Journal ofGenetics, 4.- - and Pease, M . S., T930. Genetic studies in poultry, V II I. On a case ofsex-linkage wi thin a breed. J ournal uf Genetics, 22 .Robcrt s, ] . A. F. , an d Cr ew, F. A. E., 1925. The gcnetics of the sheep , Bibliographia Genetica (T he Hague), 2.Sandcrs, H . G., 1928. The varia tion in milk yields caused by season of theyear, service, age and dry pe riods and their elimination. Journal ofAgricultural Science, 18.


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The Application 01Science to AnimalBreedingSmith, A. D. Buchanan , 1931. The average agcs oEcows and bulls in six brecdsof caule. Journal rifAgricultural Science, 2 I .Thomson , W., and Fraser, A . H. Ho, 1939 . Fceding concentra tes to the in lamb ewe. Scottisli J ournal rifAgriculture , 22.Vergcs, j . B., 1939. (a) Effcct of nutrition on the carease quality of Suffolkcross lambs. Yearbook SujJolk Sheep Society, I pswich .--, 1939. (b) The effect of plane of nutrition of th e ewe on weight anddcveloprnent of the lamb at birth. Proceedings o the Fourth InternationalCongress Animal Breeding, Zrich.Wa Ilacc , L. R o, 1944 Feeding during pregnancy. Proceedings ofthe Brilish Societyof Animal Production, seco nd meeting .Walton , A., 1930. The efect of tempcrature on the survival in vitro of rabbitsperrn ob tain ed Irorn th e vas dcfcrcns. Journal ofExperimenta! B iology, 70- - and H ammoncl, j . , 1938. T he maternal effects on growth and con formation in Shi re ho rse-Shetl and pony crosses. Proceedings o the Royal Soc ieiy(Biological) , 125.-- and Prawochenski, R. , 1936. An experimen t in eutelegencsis. Journal ofHeredity, 27Wilso n , j . , 1909 . The or igin of Dexter-Kerry brced of cattIe. Scieniific Proceedingsof the RO'a! Dublin Society, 1 2 .-- , 1910. The Eoolution of Britisli Cal/le and the Fashioning oj Breeds, London.Wood, T. B., 1g09. The inheritance of horns and face colour in shecp . J ournalof Agricultural Science, 8.Wright , N. C., 1933. Wastage in dairy COWSoScottish J ournaloj Agriculture, 16.

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The Science of Animal Breeding in Britain