708 EXPERIMENTAL EPIDEMIOLOGY.-SCARLATINAL OTITIS

and explanation can be brought into harmony.Observation has its limits of usefulness in unravellingsuch problems ; there is, indeed, little hope of successunless the questions can be dissected and simplifiedby experiment. The recent progress of experimentalepidemiology, associated chiefly with the work ofProf. W. W. C. TOPLEY in this country and of Dr. L. T.WEBSTER in America, is, therefore, to be heartilywelcomed and their work deserves close study. Inthe latest instalmentl of the Manchester work thecareful experiments made by Prof. TOPLEY are

analysed and discussed by Dr. M. GREENWOOD as if

they were the returns of a medical officer of health, andtheir joint paper makes an exceptionally readableand interesting document. The particular infectionexamined is the pasteurellosis of the mouse, and theparticular problem here dealt with is the effect of

adding normal animals to an infected population. Ithad previously been shown that if an epidemic isstarted in a mouse community it spreads throughit and then dies away, leaving a certain number ofsurvivors, and that if at this stage a number of normalanimals are added to the community the epidemicblazes up again and involves not only the fresh micebut also the survivors of the first outbreak. In thepresent experiments fresh normal animals were addedat various intervals of a few days, and in this way anepidemic was maintained for more than three years.The mortality was not regular but in waves, usuallyof a length of about three weeks, though sometimesthree times as long, and the course of the mortalityvaried with the number of fresh mice coming intothe population and the rate at which they came in.The outstanding fact, as the authors point out, isthe encouragement of an epidemic in a communityby the immigration of non-infected individuals. Ithas generally been assumed that the admission ofnormal animals to an infected herd is not dangerousto that herd (though it is, of course, dangerous to thenormals coming in). This is shown to be unsound.The explanation remains to be worked out. Atpresent one can assume only that in the decline ofan epidemic some sort of balance is reached betweenthe parasites and the hosts such that the parasitescan do no further harm unless they can get into somenormal non-immune individuals in whom they canbreed up a race which is capable of attacking theresistant residue of the epidemics. These are questionsat the very fundamentals of epidemiology, and wemay look to the experimental method to help sub-stantially towards their solution. Meanwhile we may reflect on the wisdom of the ancients who knew that the best thing to do with an epidemic was to shut it up and have nothing to do with it. vVe now know ]that they were thinking of others as well as of themselves. ’

. a

SCARLATINAL OTITIS.Mr. T. B. LAYTON’S report 2 two the Metropolitan

Asylums Board on ear disease in scarlet fever is acontinuation of that sent in by him in July, 1921, asa result of one year’s work, and the present reportdeals with the 13 months from September, 1923,to September, 1924, inclusive. In that period 290 scarlet fever patients suffered from suppurative disease of the middle ear, a percentage of 8-61 ; .the incidence in scarlet fever of simple type was 7-13, , and in septic scarlet fever 24 per cent. ; the statistical , tables also show that otitis is more frequent, and

1 Journal of Hygiene, 1925, xxv., 45.2 M.A.B. Annual Report. 1924-25. Pp.187-217.

recovers less rapidly, in the first quinquennium than. at a later age. Mr. LAYTON refrains from giving an

opinion as to the potential infectivity of the ear

discharge, and refers to the awkward position whichmight occur if a mastoid operation were advised ata fever hospital, because the discharge is a dangerto others, rather than for the welfare of the patient.The conclusions at which he arrives in regard totreatment are not always in accordance with thepractice accepted in general otological work; butit must be remembered that the management ofscarlatinal otitis, especially in institutional treatment,differs from that of otorrhcea in general practice.

Paracentesis of the drum was only performed26 times out of a total of 379 ears in which dischargeoccurred ; this low figure is partly due to the absenceof symptoms, for pain is far less frequent than inordinary otitis, and routine inspection of the ears

in the absence of symptoms is hardly practicable inlarge institutions ; but chiefly is it due to the shortperiod that elapses between bulging and rupture.In fact, the difficulty is to ensure the operation beingcarried out in time under the conditions whichregulate its performance in the Board’s infectioushospitals, the time necessary to obtain the consentof the parent being, in many cases, responsible forthe delay. This is an administrative difficulty whichwould not occur in private practice and might perhapsbe obviated by an alteration in the regulations; in

any case, it does not detract from the value of theoperation, when it can be performed, a value ofwhich Mr. LAYTON is firmly convinced, though thisis the one point on which his Board do not agree withhim. A remarkable point is Mr. LAYTON’S tribute tothe value of Wilde’s incision ; this operation wasperformed 16 times ; eight cases left the hospitalswithout any further operative treatment and withdry ears. Of these Mr. LAYTON says that " under anyother plan all these children would have been sub-mitted to the complete mastoid operation ’’ ; thisremark is inaccurate, as by the " complete " is usuallymeant the " radical " mastoid operation, but pre-sumably he means antrotomy, and his statement that" they would not have shown a better result isjustified. Of these eight cases one was aged 6 andone aged 5 ; none of the others was over 3 years old.But the other eight cases, of whom five were under4 years of age, were later submitted to a mastoidoperation ; of these, one died from septicaemia andtwo left hospital with active disease still present.This result must be considered good ; if 50 per cent.of acute otitis with retro-auricular swelling in youngchildren can be got well with Wilde’s incision, it ispossible that as good results might be obtained inion-searlatinal cases, at any rate under the age oft years. Surprisingly poor results are shown byantrotomy performed for ear discharge only; ofsix cases the first alone was a complete success; thesecond, operated on two months after onset, remainedvith a moist perforation ; and the third, operatedm after three months, with a discharging ear; theother three are catalogued as failures, but the date ofoperation is not mentioned. This is in marked contrasto the results obtained in ordinary otological practice,vhere operation after two or three weeks is usuallyuccessful ; the date of operation is only given inhese two cases, but it is possible that better resultswould have been obtained if they had been operatedn sooner. Mr. LAYTON’S opinion is that those caseso badly which show no signs of disease in the mastoidt operation, that it is impossible to distinguish byrdinary examination which cases have disease inie mastoid, and that an X ray examination is likely

709LOCAL ANESTHETICS AND CHEMICAL CONSTITUTION.

to be helpful in this respect. Accordingly he hasrecommended to the Board that an X ray apparatusbe installed at one of the fever hospitals for examina-tion of the mastoids of these cases, and this the Boardhas agreed to do at the North-Eastern Hospital.An important problem is presented by the cases

discharged with active otorrhcea ; there were 35 ofthese, of whom 17 had discharge before contractingscarlet fever. Of the remaining 18 cases, 11 had

Ieither septic scarlet fever or a mixed infection, leavingseven only of the ordinary type of scarlet fever.Surely no better tribute to the excellence of the

management of these three hospitals could be desiredthan that only seven cases contracted an uncuredscarlatinal otitis in the 13 months under review. But itis naturally desired to reduce the number still further ;recognising that scarlet fever leaves the patient with a resistance profoundly lowered to the ordinary organisms of suppuration, Mr. LAYTON believes that 1heliotherapy should be employed, and the Board hasadopted his suggestion, and proposes to set apart a (ward of 12 to 20 beds for experimental sunlight treatment with an ultra-violet apparatus for use on idull days and during the winter months. Needless s

to say, the result of the treatment of pyogenic infec- s

tions, in cases of lowered resistance, by this method twill be watched by those interested in many different c

departments of medicine and surgery. c

Annotations.

LOCAL ANÆSTHETICS AND CHEMICAL

CONSTITUTION.

"Ne quid nimis."

LOCAL anaesthetic substances have hitherto usually Ibeen employed in the form of hydrochlorides whichhave a definite acid reaction and are largely ionisedin solution. Such solutions are fairly satisfactoryin producing local anaesthesia when injected, parti-cularly in conjunction with adrenalin, but they havelittle surface anaesthetic action, and on this accounthave not proved satisfactory substitutes for cocainein ophthalmic surgery. For this surface action the

s carried out in conjunction with Mr. H. E. F. Notton,; B.Sc., at the laboratories of pharmacology and- chemistry of the University of Cambridge, is now setout at length in the British Medical Journal for

Sept. 26th. The borates show the desired surfaceaction in a high degree, and the local anaesthetic

action of a large number of them has been measured.

on the cornea of the rabbit. In this way several ofthese borates were found to have a surface anaes-

thetic action equal to, and in some cases greater than,that of cocaine hydrochloride. Owing to the satis-factory results obtained with the borate of " etho-caine " (of which novocaine is the hydrochloride),special attention was paid to this substance. Notonly has it a stronger surface anaesthetic action thanmost of the borates tested, but it also has the advantageof greater stability. It acts rapidly, both as a surfaceand a hypodermic anaesthetic, its surface action beingmore powerful than that of cocaine hydrochloridein solutions of equivalent concentration. It is prac-tically free from any toxic action, and is non-irritant.Its solutions keep well and do not precipitate incontact with the tissues and body fluids. It is, aswould be expected from the salt of a moderatelystrong base with a very weak acid, slightly alkalinein solution, the alkalinity of the solutions of thestrength used being equivalent to pH 8. This sub-stance, ethocaine borate, is now manufactured bythe British Drug Houses, Ltd., and is available forclinical use under the name " borocaine." Forconvenience it is supplied in tablets together witha small quantity of adrenalin and sufficient sodiumchloride and pure glucose to make an isotonic solu-tion when dissolved in the prescribed quantity ofsterile water to make a 2 per cent. solution, this beingthe usual strength for producing surface anaesthesia.Of the other borates that of &bgr;-eucaine is the mostnoteworthy, as it has the highest surface anaestheticpower of all. Further information concerning thisinteresting and possibly very valuable substancewill be welcomed.The local anaesthetics form a very interesting group

from the point of view of the relation between chemicalconstitution and physiological action. Although thefirst substance to be widely used as a substitute forcocaine itself, a-eucaine has a structure somewhatresembling that of cocaine, it was soon replaced by&bgr;-eucaine, which has a structure less like that ofcocaine, and subsequent developments were concernedentirely with substances, such as anæsthesine, novo-caine, butyn, stovaine, tutocaine, &c., which have

free base appears to be far superior to the ion, andsubstances which undergo hydrolytic dissociationare greatly to be preferred to those undergoingelectrolytic dissociation. Salts formed by combina-tion of the base with weak acids when dissolved inwater undergo very little ionic dissociation and muchhydrolytic dissociation, and hence show the strongsurface anaesthetic action of the base itself. Atthe time of the Bath meeting of the British MedicalAssociation Dr. A. J. Copeland communicated 1the results of experiments and tests, made by himas Ernest Hart Memorial Scholar, with the borates ofthese local anaesthetic bases. The work, which was

1 THE LANCET, 1925, ii., 196.

I very little resemblance at all to cocaine from thestandpoint of chemical structure. It is very curious

in this connexion to note that a-cocaine resemblescocaine itself in structure far more closely than does

i a-eucaine, but differs from these in being quitei devoid of local anaesthetic action. The more recent; local anaesthetics of the ethanol, propanol, and butanol

series, such as novocaine, butyn, and tutocaine, arel of simpler chemical structure than cocaine, thoughclosely related to one another, as can be seen fromthe structural formulae of many of these compoundsgiven by Mr. E. Watson-Williams in a recent account 2of the pharmacology of tutocaine.

2 THE LANCET, 1925, i., 914.