320 RETROGRESSIVE CHANGES 



to that of cheese. If we bear in mind the fact that cheese is a 

 mixture of coagulated proteid and finely divided fat, and that 

 in caseation we have a coagulation of tissue proteids associated 

 with the deposition of considerable quantities of fat, the reason 

 for the gross resemblance of the product of this form of necrosis 

 to cheese is apparent. Schmoll l has analyzed caseous material, 

 and found it almost entirely free from soluble proteids or prote- 

 oses. The proteid material is almost solely coagulated proteid, 

 which in its elementary composition is related to the simple 

 proteids or to fibrin, and not at all to the nucleoproteids. The 

 extremely small amount of phosphorus present in the caseous 

 material indicates that the products of disintegration of the cell- 

 nuclei must diffuse out early in the process. Caseation is, there- 

 fore, characterized by a coagulation of the proteids and a dis- 

 solving out of the nuclear components. Schmoll does not 

 explain the cause of coagulation, however. It may be that it 

 is the same as in the coagulation of anemic infarcts (since 

 tuberculous areas are decidedly anemic), or possibly the tuber- 

 cle bacillus produces substances coagulating proteids, as Ruppel 2 

 states is the property of " tuberculosamin." Indeed, Auclair 3 

 claims that the fatty substance that can be extracted from 

 tubercle bacilli by chloroform is the cause of the caseation. 

 Dead tubercle bacilli do not produce true caseation, however, 

 according to Kelber 4 ; hence the substance causing the necrosis 

 evidently does not diffuse readily from the bodies of the bacilli. 

 The abundance of fat in caseous material is very striking. 

 Bossart 5 found from 13.7 per cent, to 19.4 per cent, of the dry 

 substance of caseous material soluble in alcohol and ether. In 

 the scrapings from tuberculous bovine glands I have found 22.7 

 -23.9 per cent, of the organic material soluble in alcohol and 

 ether. 6 Of this soluble material, Bossart found 25 to 33 per 

 cent, of cholesterin, and Leber 7 found 38.31 per cent, of leci- 

 thin, which is a much higher proportion than Bossart detected. 

 Presumably these fatty materials are derived chiefly from the 

 disintegrated cells ; this is probably true of the lecithin and 

 cholesterin, but the fact that in histological preparations most 

 of the fat is found about the periphery of the caseous area, 8 



1 Deut. Arch. klin. Med., 1904 (81), 163. 



2 Loc. cit. 



3 Arch. meU exper., 1899, p. 363. 



* Quoted by Diirck and Oberndorfer, Ergebnisse der Pathol., 1899 (6), 288. 



5 Quoted by Schmoll, loc. cit. 



6 Wells, Jour. Med. Research, 1906 (14), 491. 



7 Quoted by Schmoll. 



8 Sata, Ziegler's Beitr., 1900 (28), 461. 



