EXPERIMENTAL PRODUCTION OF FAT NECROSISFAT NECROSIS ABOUT THE PANCREAS OF THE HOG

HERBERT U. WILLIAMS, M.D.From the Pathological Laboratory of the University of Buffalo

Reprintedfrom the Boston Medical and Surgical Journal of April 15, iBqy.

THE EXPERIMENTAL PRODUCTION OF FAT NECROSIS: FAT NECROSISABOUT THE PANCREAS OF THE HOG.

HERBERT tT. WILLIAMS, M.D., BUFFALO, N. Y.,From the Pathological Laboratory of the University of Buffalo.

The relationship of fat necrosis to affections of thepancreas, and especially to pancreatitis, has beendemonstrated by Fitz, 1 but the significance of thisconnection is not clear. The essential change in fatnecrosis is a decomposition of the neutral fat mole-cule into its component fatty acid and glycerine. Fre-quently, if not always, the fatty acid unites with cal-cium to form a new compound, which is a soap. It isremarkable that the fat-splitting ferment of the pancreasaccomplishes this very decomposition of neutral fats.Certain experiments reported within the last few yearsseem likely to put us in the way of demonstrating theexact nature of the connection between fat necrosisand affections of the pancreas.

Hlava, 2 excited a hemorrhagic pancreatitis with fatnecrosis in a cat by injecting the diphtheria bacillus intothe pancreas after laparotomy.

Langerhans,8 suggested that the decomposition ofneutral fats which occurs in this process might be ac-complished by the fat-splitting ferment of the pancreas.He announced that he had succeeded in producing fatnecrosis in a rabbit. This was the only positive resultamong twelve animals (rabbits and dogs) experimentedupon. He made use of a suspension of rabbit’s pan-creas in distilled water, which was injected into theadipose tissues. His positive experiment is open tothe objection that bacterial contamination was not ex-cluded with certainty.

Hildebrand,4 and his student, Dettmar, placed a liga-ture about the gastro-splenic portion of the pancreas,to prevent the discharge of its secretion through theduct, in two cats ; and in six others they performed thesame operation and also ligated the veins leaving theorgan. In all cases fat necrosis was found about thepancreas. They were also successful in producing itthree times by introducing portions of the pancreas ofone cat into the abdominal cavity of another. In oneinstance they obtained it after removing a piece fromthe organ and leaving the distal portion without liga-ture. Hildebrand, furthermore, injected pure trypsininto the abdominal cavity, and found that hemorrhagesinto the peritoneum resulted. He suggested that thehemorrhages, so frequent in pancreatic affections,might be due to the action of trypsin, while the fat-splitting ferment was responsible for fat necrosis.

1 Fitz : Proceedings New York Pathological Society, 1890. BostonMedical and Surgical Journal, 1889. Medical Record, 1889. MedicalNews, Philadelphia, 1889. Transactions Association American Physi-cians, 1890.

3 Hlava: Sbornik Lekarsky (Archives bohemes de mddecine) vol.iv, 1890 (synopsis in French).

3 Langerhans, K : Experimenteller Beitrag zur Fettgewebsnekrose.Festschrift, K. Virchow, Berlin, 1891.4 Hildebrand: Centralblatt filr Chirurg., 1895, vol. xxii, p. 297 ; alsoreport Cong. Deutsche Gesellsch. fiir Chirurg., same journal. Dett-mar : Inang. Diss., Gottingen, 1895.

Dr. Whitney, of the Harvard Medical School, allowsme to state that he ligated the pancreas in a numberof dogs and produced fat necrosis in one of them. Noaccount of his work has been published.

Rosenbach, and his pupil Jung,5 with a similar ob-ject in view, introduced trypsin and at other times por-tions of pancreas, into the abdominal cavities of rab-bits. Out of four trials with pieces of pancreas iheyobtained fat necrosis once, using dog’s pancreas.

As the work of Hildebrand has seemed to have beenthe most productive of results, the writer has attemptedto verify his conclusions. The animals selected weretwo dogs, one rabbit, and seventeen cats. They wereanesthetized with ether. The operations consisted inthe placing of a ligature about the gastro-splenic por-tion ©f the pancreas near the duodenum, or the duodenalportion of the pancreas, or both. In most cases asmany as possible of the veins leaving the pancreaswere also tied. In the majority of cases a solution ofcontinuity in the pancreas was effected. In one in-stance the gastro-splenic portion of the pancreas wascut through on the distal side of the ligature. Anaseptic technique was followed, and the results weregood with the exceptions noted below. The peri-toneum and skin were closed separately with silksutures. The wounds in the abdominal walls fre-quently furnished slight purulent discharges. Owingto the freedom allowed to the animals it was foundimpossible to secure primary union in every instance.Animals that died during the first twenty-four hoursafter operation were not included in this report.

The operations and their results in detail were asfollows:

Dog. Weight 7 lbs., oz. A silk ligature was tiedabout the gastro-splenic portion of the pancreas. The ani-mal, while apparently in perfect health, was killed at theend of one week ; weight 8 lbs., oz. There was no peri-tonitis and no fat neci'osis.

Dog. Large, fairly nourished. The gastro-splenic por-tion of the pancreas was ligated. The dog was killed afterten days, somewhat emaciated. There were adhesions andsuppuration about the ligature, but no general peritonitis.There was no fat necrosis.

Rabbit. Moderately fat. The gastro-splenic portion ofthe pancreas was ligated. The animal remained in goodcondition, and was killed after three weeks. There wasno peritonitis. There were traces of fat necrosis close tothe ligature.

From the seventeen cats there were ten negative re-sults. In two there were minute areas probably of fatnecrosis. In five there was well-developed fat necrosis.

5 Jung: Inaug. Diss., Gottingen, 1895. Be£. in Centralblatt furChirurg., 1895, vol. xxii, p. 310.

2 THE EXPERIMENTAL PRODUCTION OF FAT NECROSIS.

One of the five exhibited disseminated fat necrosis. Indetail, the operations and results were as lollows :

Cat 11. Weight 6 lbs., 14 oz. The gastro-splenic por-tion of the pancreas was ligated. The animal was killed atthe end of one week; weight G lbs., 5 oz. There was nofat necrosis nor peritonitis.

Cat 8. Weight 4 lbs., 1 oz., but fat. The gastro-splenicportion of the pancreas was ligated. The animal, while ap-parently healthy, was killed after one week; weight 4 lbs.,2J oz. There was no peritonitis. Small nodules of fatnecrosis were discovered at the interlobular pancreatic fatand in the omental fat. 'There was one nodule in the peri-renal fat (Fig. 1), and one in the mesorectum. No bac-teria could be demonstrated by staining methods in or nearthese areas.

Cat 6. Weight 7 lbs., 10 oz., well nourished. Thegastro-splenic portion of the pancreas was ligated. Thecat was killed after two weeks ; weight G lbs., 13 oz. Therewas no fat necrosis nor peritonitis.

Cat 7. Weight 7 lbs., 4 oz., fat. The gastro-splenicportion of the pancreas was ligated. The cat was killedafter three weeks; weight 5 lbs, 13£ oz. A few minutespots, probably of fat necrosis, were found in the omentalfat. Staining methods showed no bacteria in or aboutthem. There was no peritonitis. This was one of the twocases classed as doubtful.

Cat 4. Weight 4 lbs., 8£ oz., poorly nourished. Thegastro-splenic portion of the pancreas was ligated. The catremaining healthy was killed after four weeks ; weight 4 lbs.,

oz. There was no fat necrosis nor peritonitis.Cat 3. Weight 6 lbs., 3 oz., fat. The duodenal portion

of the pancreas was ligated. The cat was killed after oneweek, then seeming to be in good condition. There wasno peritonitis. Traces of fat necrosis appeared close tothe ligature. This was the second of the two cases classedas doubtful.

Cat 13. Weight 5 lbs., oz. Both the gastro-splenicand the duodenal portions of the pancreas were ligated, andas many as possible of the veins leaving the gastro-splenicportion were tied, and the continuity of the tissue of thepancreas was broken by a sharp hook passed into it be-neath the peritoneum. The animal died after four days,being much emaciated. The autopsy was unavoidably de-layed till about thirty-six hours after death. There was noperitonitis. There were several thin, flat areas of fat necro-sis on the surface of the omentum. The mucous membraneof the pyloric end of the stomach showed a number ofsmall round excavations having all the characteristics ofpeptic ulcers. All the peritoneal surfaces were abundantlycovered with large bacilli, stained by Gram’s method. Norelation in their distribution to the spots of fat necrosiscould be made out. Similar bacilli were present in largenumbers on the mucous membrane of the stomach and duo-denum, extending into the subperitoneal tissues and aboutthe pancreas. In view of the long time that elapsed beforethe autopsy was made they were not regarded as of impor-tance.

Cat 18. Both the gastro-splenic and the duodenal por-tion of the pancreas were surrounded with ligatures, aswell as the veins leaving the former. The cat died afterforty-eight hours. There was no fat necrosis nor perito-nitis.

Cat 19. The operation and result were similar to thosein Cat 18.

Cat 21. Weight 4 lbs., oz. The gastro-splenic por-tion of the pancreas was ligated and as many as possible ofthe veins issuing from it, and the substance of the organwas broken with a hook. The animal died after four days;weight 3 lbs., 11£ oz. The autopsy was made in less thantwenty-four hours. The peritoneal surfaces were coveredwith a fibrinous exudate. Beneath the peritoneal exudatea few thin, flat, white areas were seen, which proved to benecrotic adipose tissue. The exudate contained great num-bers of diplococci and fewer large bacilli, both staining byGram’s method. The diplococci alone were recovered incultures. They grew feebly, not liquefying gelatine, and

very quickly died out. In sections, no grouping of themicro-organisms with reference to the spots of fat necrosiscould be demonstrated.

Cat 22. Weight 4 lbs., 13| oz., not fat. The gastro-splenic portion of the pancreas and the veins leaving itwere ligated, and its substance was injured as in the othercases. The wound in the abdominal wall suppurated. Thecat was killed on the fifth day after the operation; weight4 lbs. At the autopsy, which was made immediately, thewriter was astonished to find in the abdominal cavity a con-dition of disseminated fat necrosis comparable to that oc-curring in man. In the vicinity of the pancreas, the retro-peritoneal and omental fat was swollen, white and opaque,over an extent reaching twelve millimetres or more fromthe pancreas, and radiating from it in irregularly shapedmasses. Smaller areas of similar character were scatteredin great numbers through the omental fat and that of themesentei’y along its entire length, even to the mesorectum.They occurred also in the perirenal fat. There was noperitoneal exudate. The animal was nevertheless the sub-ject of an infection, proceeding no doubt, from the woundin the abdominal wall. The pus in this wound contained avariety of organisms, among them diplococci and largebacilli. Although examination of cover-slips was nega-tive, cultures from the spots of fat necrosis and from theliver yielded diplococci or short streptococci, growing atroom temperature, not liquefying gelatine, forming minutewhite circular colonies on agar, and staining by Gram’smethod. Cultures from the pancreas and the blood of theright heart were negative. The distribution of the necroticspots, especially of those in the mesentery, made them ap-pear suspiciously like minute abscesses, but the microscoperevealed their true character. In a section of the mesen-tery, diplococci were found in and about one of the areasof fat necrosis, and also, in smaller numbers, at points inthe mesentery remote from it. Otherwise, the examina-tions of sections of the necrotic areas for bacteria were neg-ative.

Cats 27, 29, 31, 32 and 36 were good-sized and healthy.In each case the splenic portion of the pancreas was con-stricted by a ligature near the duodenum, as many as possi-ble of the veins leaving it were tied, and the tissue of thepancreas was disturbed as in the other cases. The animalsall made good recoveries. Their abdomens were opened atperiods varying from eight to seventeen days. There wasno peritonitis, and no fat necrosis in any case.

Cat 34. Large and rather fat. The splenic portion ofthe pancreas was ligated near the duodenum, and the pan-creas was then cut completely through on the distal side ofthe ligature, with the intention of allowing its secretion toflow into the peritoneal cavity. The animal died at theend of a week. The autopsy was made eighteen hoursafter death. The peritoneal sutures were found to havegiven way. The abdominal cavity contained a quantity ofpinkish-white turbid fluid. The peritoneal surfaces werecongested and covered with a thick layer of fibrin. Thefat tissue of the omentum appeared swollen and edematous.Irregular white patches of necrotic fat tissue were seen inthe omentum and in the vicinity of the splenic portion ofthe pancreas, especially near the cut extremity. Smearsmade from the peritoneal exudate showed it to containmany large bacilli, and minute cocci. Cultures made fromthe peritoneum, the viscera, and the blood gave only minutewhite colonies of diplococci, staining by Gram’s method,lancet-shaped, and like the diplococcus of pneumonia in form.Sections of the necrotic fat tissue and of the pancreasexhibited great numbers of large bacilli and diplococci, bythe Gram-VVeigert method, mostly on the surfaces, and notshowing any special relation to the areas of fat necrosis.Sections of the pancreas demonstrated necrosis of the fatcells about it and in the interlobular septa in a strikingmanner.

In all of the animals studied, the diagnoses werebased on the microscopic examination of the tissues,which is indispensable. Many pictures of great beautyillustrating the condition were obtained. The tissues

THE EXPERIMENTAL PRODUCTION OF FAT NECROSIS. 3hardened in alcohol were found to be very .welladapted for histological purposes. A five-per-cent,solution of formalin in normal salt solution preservedthe macroscopic appearances more satisfactorily, butthe writer has given up using it when the minutestructure is to be studied. One-per-cent osmic-acidsolution makes an excellent hardening agent, as thenecrotic areas are not stained black by osmic acid.The areas of fat necrosis were sometimes roundedand nodular, about one to two millimetres in diameter;sometimes they were broad and thin. They occurredexclusively in the fat adjacent to the peritoneum,usually in immediate contact with it. A dispositionof the necrotic process to affect the vicinity of theligatures about the pancreas or the veins was noted,but it was not constant or very marked. In recentlykilled animals the recognition of the areas was easy,owing to their opacity, contrasting with the rela-tively transparent normal fat. When a peritonealexudate was present, it was often difficult to recognizethem beneath the layer of fibrin.

In frozen sections the areas were opaque, contrast-ing with the neighboring fat (Fig. 2). A brown tingewas often visible. Such complete disorganization ofthe adipose tissue as occurs in the human subject wasin no instance observed. The areas consisted ofrounded bodies similar in outline to the fat cells. Inmost cases the contents of these bodies were minuteneedle-shaped crystals. Frequently the crystals werearranged in a radial manner at the circumference ofthe circle. The central portion was then empty orcontained oil droplets. Such bodies in transverse sec-tion appeared as rings (Fig. 4). Calcium salts weredemonstrated in some nodules in abundance. Thecontents of the necrotic cells in balsam preparationsusually appeared homogeneous, although their cystal-line nature was sometimes discernible. They reactedvariously with stains, in some instances showing an af-finity for eosin, in others staining deep blue with hema-toxylin. The paore intense hematoxylin stain notedin some nodules the writer supposes to have been dueto an abundance of calcium salts. The nuclei of thenecrotic cells could not be identified. The amount ofcell infiltration about the nodules of fat necrosis wasquite variable. In some examples it was very slight,more often it formed a distinct band about the circum-ference where it was mingled with granules most ofwhich stained deeply with nuclear dyes. Frequentlyit passed widely into the surrounding tissues. Thecells were in large part polynuclear leucocytes. Inpart they were larger, mononuclear elements roundedor spindle-shaped in form, with round or oval nuclei.They generally were of moderate size, though quitevariable in this respect. Fragmentation of nuclei wasa prominent feature in this zone, the fragmentationbeing most extensive in the part immediately adjacentto the necrotic fat.

In and around the areas of fat necrosis numerousgranules and rounded masses occurred, staining withcarmine, hematoxylin, and by the Gram-Weigertmethod. Some of these were evidently fragmentednuclei; others were hyaline in character ; others, whichstained very deeply with hematoxylin, were supposedto contain calcium. These granules were often sonumerous as to obscure the nuclei at the margin ofthe area. They rendered the search for bacteria insections difficult and unsatisfactory.

The changes taking place in the pancreas were

studied only with reference to the question in band,and the account of them must be brief. The ligaturesabout the pancreas were found enclosed in a zone ofleucocytes or good-sized mononuclear cells, or both,and often also of fibrous tissue. The cell infiltrationfrequently passed into the interlobular connective tis-sue of the pancreas and over its surface. Jn the ani-mals that were allowed to live longest there weremarked atrophy and induration of the ligated ex-tremity of the organ, which the microscopic examina-tion showed to be due to an atrophy of the acini andan abundant formation of fibrous tissue between thelobules, and even between the acini. Desquamationof the epithelial lining of the ducts was of frequentbut not invariable occurrence. There was less dilata-tion of the ducts on the distal side of the ligature thanone might have expected to encounter. The writer isunable to say with confidence that there was more in-terstitial pancreatitis or any other characteristic mor-bid condition of the pancreas in the animals thatshowed fat necrosis than in those that did not.

In nearly all cases sections of the liver, spleen andkidneys were examined, but no alteration was discov-ered that appeared to have any relation to the questionin hand. No tendency to hemorrhages of a marked orconstant type was noted in any of the tissues. Theurine was examined for sugar in the majority of cases,and none was found.

Although the writer has been less successful thanHildebrand, his work renders it evident that ligationof the pancreas in the cat may lead to fat necrosis.As far as he is aware, Cat 22 of his series exhibitedthe most extensive fat necrosis that has been recordedas having been produced by artificial means. Thesimultaneous existence of a diplococcus infection, inthis animal and in Cats 21 and 34, is noteworthy.It is significant that the areas of fat necrosis were ob-served only in close connection with the peritonealcavity, and especially in the neighborhood of the pan-creas, which would make contact of the pancreaticjuice with these areas intelligible. The circumscribedcharacter which they usually exhibited and their oc-currence at points remote from the pancreas are diffi-cult to account for. It seems unjustifiable at presentto say more than that extensive injury to the pancreascan cause fat necrosis.

The writer has been conducting experiments with aview to testing the direct action of the excised pan-creas upon fat tissue. He believes that he has suc-ceeded in producing fat necrosis in this manner. Theconditions under which the change is effected are notyet clear, and any account of this work at presentwould be premature. A single one from this seriesmay be related here, however, not to illustrate thedirect action of the ferment artificially introduced,but to show the effects of a pancreatitis excited byaccident.

Cat 15. Large and healthy. The abdomen was opened,a piece of pancreas 20 m. m. in length just removed fromanother cat was fastened to the omentum with a silk liga-ture, and the abdomen was closed. The animal died aftersix days. The autopsy was made twenty-four hours afterdeath. A fibrinous exudate covered all the peritoneal sur-faces. The effect of the piece of pancreas introducedupon the adjacent omentum was not clear. A small areaof fat necrosis was discovered on the surface of the leftkidney, and others were seen in the omentum. Section ofthe animal’s own pancreas showed an acute pancreatitis,apparently originating by extension inwards from the in-

4 THE EXPERIMENTAL PRODUCTION OF FAT NECROSIS.

fected peritoneum, which the exposed condition of thepancreas in the cat makes possible. Fat necrosis wasseen in a large part of the fat tissue in immediate contactwith the inflamed pancreas, and the connection betweenthe two was demonstrated in a convincing manner, Cover-glass preparations, sections and cultures showed a largebacillus and a small diplo- or strepto-coccus, both stainingby Gram’s method, in the peritoneal exudate, and in thepancreas.

In this case, the conditions seem to be practicallythe same as those obtained by Hlava when pancreatitisand fat necrosis followed from the injection of thediphtheria bacillus into the pancreas. The possibilityof their occurring ought to be borne in mind whenpieces of pancreas or pancreatic extracts are intro-duced into the peritoneal cavity in experimentalstudies.

In connection with this work the writer has exam-ined the pancreas and peritoneal adipose tissues ofabout forty cats. Quite early one was encounteredexhibiting spontaneously minute white spots in theomental fat, not near the pancreas however, which onsection resembled closely very small areas of fat necro-sis. Recently a similar condition has been found in asecond cat (Cat 37).

The animal was very fat. The abdomen was openedwith a view to operating on the pancreas, when the adiposetissue of the omentum was observed to contain about tenirregular, opaque, white areas, approximately one-fourthof a millimetre in diameter. They were not observed inthe vicinity of the pancreas. Two of these areas and asmall bit of the pancreas were removed for examination,and the abdomen was closed again. Sections of the pan-creas exhibited nothing remarkable. One of the suspiciousareas in the omental fat, under the microscope proved tobe opaque; after slight pressure it broke into irregular,translucent masses with a brown tinge, and made of fine,radiating crystals. Upon the warm stage, after the addi-tion of glacial acetic acid, the brown masses dissolved ; atthe same time there was a noticeable evolution of oildroplets, apparently from the brown masses. The smallsize of the suspected areas made removal beforehand ofthe free fat with boiling alcohol and ether impossible. Sub-sequent neutralization and addition of oxalic-acid solution,produced an abundant precipitate of calcium oxalate crys-tals. Thin sections stained in hematoxylin showed thearea partly surrounded by good-sized mononuclear cells,which, along with a small amount of fibrous tissue, partlypenetrated its interior.

The condition seemed to be one of fat necrosis aris-ing spontaneously in the cat and probably not recent(Fig. 3). If it depended upon any morbid state ofthe pancreas, that had apparently subsided. The ani-mal made a good recovery. It is now, after tenweeks, still healthy. The intention is to observe theprogress of events after the lapse of a longer period.

FAT NECROSIS IN THE PANCREAS OP THE HOG.

Balser,6 who was the first to describe fat necrosis inthe human subject accurately, was also the first tostudy its appearance in the hog in detail. He foundit in the fat tissue in or about the pancreas in nearlyall Hungarian swine, frequently in Algerian, and in afew German swine. He found in the necrotic nodulesbodies resembling the fungus of actinomycosis. Inorder to determine whether or not fat necrosis oc-curred in American hogs the writer examined the pan-creas of one hundred hogs. It was impossible tolearn anything more concerning the animals than that

6 Balser : Yerhandl. d. XI Cong, f. innere. Med., Wiesbaden, 1592,p. 450.

they were raised either in Ohio, Indiana, Illinois orMichigan, and were apparently sound and healthy.The pancreas of the hog is surrounded by a quantityof adipose tissue, which is also abundant between thelobules. The fat cells are very large. Little whiteflecks consisting of single fat cells or groups of fatcells are often seen in the pink parenchyma. Notrarely one meets with dark red spots in the parenchyma,several millimetres in diameter, apparently the resultof hemorrhage. The organ, taken as fresh as possi-ble, was cut in slices one to three millimetres thick,and each slice carefully examined. In two cases fatnecrosis was found.

In one of these the number of areas of fat necrosis wasnot large and they were confined to a limited region. Inthe other they were numerous and were scattered through-out the organ. They were not conspicuous, being distin-guished by their more yellow color, which contrasted withthe white, normal fat. They appeared much like minuteabscesses, but were somewhat harder than the normal fat.In shape they were irregular. Their various dimensionswere one to two millimetres only. They nearly alwaysimpinged on one side against a portion of the parenchyma.Frozen sections showed them to be made of fat cells, ren-dered opaque by the presence of numerous needle-shapedcrystals, frequently arranged in the form of a ring aboutthe circumference of the cell. They contained an abund-ance of calcium. Sections stained in hematoxylin andeosin gave about the appearances already described forthe cat (Fig. 4). The contents of the areas exhibitedusually a strong blue stain. The borders were surroundedby a band of connective tissue with numerous connective-tissue cells, and a small number of polynuclear leucocytes.Leucocytes also occurred in small numbers among the cellsof the necrotic areas. Often they were in rounded clumps,corresponding to the outlines of a fat cell, and suggestingthat they might havemigrated into the interior of a necroticcell. The ray fungus described by Balser after using theEhrlich-Biondi stain was not found; nor were the hemor-rhages about the necrotic areas. Examination of sectionsfor bacteria was negative. Cultures were not made. Theparenchyma of the pancreas was not remarkable. Noneof the other organs were examined.

SUMMARY.

Among two dogs, one rabbit and seventeen cats op-erated on in the manner described there were twelvenegative, and three partly successful results. In fivecases fat necrosis of a marked type followed. Inthree of the latter a diplococcus infection was asso-ciated.

A peritoneal infection in a cat was observed to leadto pancreatitis ; which in turn produced fat necrosis.

Nodules, somewhat similar to those obtained artifi-cially, which were seen twice appearing spontaneouslyin the omentum of the cat, were possibly old fatnecroses.

Fat necrosis in and around the pancreas of the hogwas found in two out of one hundred specimens ex-amined.

EXPLANATION OP PLATES.Fig. 1. Cat 8. Borax carmine. Fat necrosis in the perirenal fat,

showing the outlines of the affected cells faintly, and cell-infiltrationabout the necrotic area (low power).

Fig. 2. Cat 22. Frozen section. Fat necrosis in the omentum,showing the opacity of the area, and the outlines of the altered cellsin it (low power).

Fig. 3. Cat 37. Hematoxylin and eosin. Supposed area of fatnecrosis in the omentum (x SO).

Fig. 4. Hog. Hematoxylin and eosin. Small area of fat necrosisclose to the pancreas (x 80).

[The writer is indebted to Dr. F. C. Busch, Assistant in the Patho-logical Laboratory of the University of Buffalo, for these photo-micrographs.]

Boston Medical and Surgical Journal. Vol. CXXXVI. No. is.

Fig. 2.Fig. 1.

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