384 RETROGRESSIVE CHANGES 



Caseous areas persist for extremely long periods of time without 

 undergoing absorption, which indicates that the autolytic enzymes 

 are destroyed early in the process, presumably b}^ the toxins of the 

 tubercle bacillus; corresponding to this SchmoU found autolysis very 

 slight indeed in caseous areas, and even wiieii tlie caseous material 

 breaks down to form a "cold abscess" the fluid differs from true pus 

 in containing less free amino-acids, e. g., tyrosine is mission.*- Be- 

 cause of a lack of chemotactic substances no leucocytes enter to re- 

 move the dead material, in consequence of wliich caseous material gives 

 no evidence of containing proteases, according to the Miiller-Joch- 

 mann ])late method. That the failure of absorption is not due to 

 a modification of the proteins into an indigestible form is shown by 

 the rapid softening of caseous areas when, through mixed infection, 

 chemotactic substances are once developed and leucocytes enter. Job- 

 ling and Petersen ^-^ suggest that in caseation the autolysis is inhibited 

 by the soaps of fatty acids, which are abundant in caseous areas and 

 have a marked antitryptic effect. 



FAT NECROSIS 83 



Through usage this term has come to indicate a specific form of 

 necrosis of fat tissue, which is characterized by a focal, circum- 

 scribed arrangement, and by the splitting of the fat in the necrotic 

 area into fatty acids and glycerol, the latter disappearing, the former 

 combining with bases to form soaps.** In practically all cases fat 

 necrosis is produced by the action of pancreatic juice upon fat tis- 

 sue,*^ presumably through the action of the enzymes it contains, and 

 the condition can be produced experimentally by any procedure that 

 causes escape of the pancreatic juice from its natural channels. 



Langerhans *^ made the first studies of the nature of the changes 

 in fat necrosis, and established the fact that the fat of the cells is 

 split into its components, and that the fatty acids combine (at least in 

 part) with calcium. Dettmer " found that, although fresh pancreatic 

 juice caused fat necrosis, a commercial preparation of trypsin did 

 not do so, and, therefore, he concluded that probably the lipase of the 



82 See Miiller, Cent. inn. Med., 1907 (28), 2!)7. 



82a Jour. Exp. I\Icd., 1914 (19), 239; Zoit. Immunitat., 1914 (23), 71. 



83 General literature will be found in tlie articles eited in tlie text : also in 

 Opie's "Diseases of the Pancreas"; and in Truhart's "Pankreas-Patliolojiie." 

 Wiesbaden, 1902. 



84 The fatty acids form masses of crystals in the fat-cells, and they can also 

 be demonstrated microcheniically by Penda's method (Virchow's Arch., 1900 ( Ifil), 

 194), which ('(msists of staininfjr with a copper acetate mixture, blue-firccii copper 

 salts of the fattv acids beini; formed. 



K-'WuHV (l?eri. klin. Woch., 1902 (39), 734) claims to have observed an excep- 

 tion. to this rule, l)ut liis accoimt is not by itself convincinii. Fabyan (.lohns 

 Hoi)kins llosp. H>ill., 1907 (IS), 349) reports a case of multiple subcutaneous 

 fat necrosis witliout pancreatic lesions, in a 14 days' old l)aby, and j^ivcs a re- 

 view of other similar cases. 



8« Virchow's Arch., 1H90 (122), 2r)2. 



8T Dissertation, Gottingen, 1895. 



