346 RETROGRESSIVE PROCESSES 



The fatty acids may be stained green by copper acetate, ac- 

 cording to Benda's method, and if then treated with hematox- 

 ylin, they turn black. 1 Fischler and Gross 2 state that fatty 

 acids are present in atheromatous areas and about the margin 

 of anemic infarcts, but are not recognizable by this method in 

 such fatty degenerations as pneumonic exudates, caseation, etc. 

 Klotz 3 considers that calcium soaps are formed as the first step 

 in pathological calcification, according to microchemical evi- 

 dence ; but a chemical investigation of the same question did 

 not give the writer positive results. 4 



PATHOLOGICAL OCCURRENCE OF CHOLESTERIN 5 



Cholesterin in crystals is found under somewhat the same con- 

 ditions as the fatty acids, and although cholesterin is not a fat, but 

 an alcohol, its physical properties are so similar that it may be con- 

 sidered in this place. (See " Gall-stones," Chap, xv, for further 

 discussion.) The characteristic large flat plates of cholesterin 

 may be found in any tissue in which cells are undergoing slow 

 destruction, and where absorption is poor. Therefore, they are 

 found frequently in atheromatous patches in the blood-vessels, 

 encapsulated caseous areas, old infarcts and hematomas, inspis- 

 sated pus-collections, dermoid cysts, hydrocele fluids, etc.; 

 especially large amounts occur in the cholesteatomatous tumors 

 of the ear and cranial cavity. 6 In liquids the crystals form 

 glistening scales ; in fresh tissues they may be recognized by 

 their solubility in ether, chloroform, hot alcohol, etc., and by 

 their color reactions. In histological specimens prepared by the 

 usual methods the cholesterin is dissolved out, but the resulting 

 clear-cut clefts are quite characteristic. In fresh specimens 

 in which cholesterin crystals are present, on treatment with five 

 parts concentrated sulphuric acid and one of water, the edges 

 of the crystals become carmine red, then violet. Concentrated 

 sulphuric acid plus a trace of iodin colors the crystals in se- 

 quence, violet, blue, green, and red. Hirschsohn 7 recommends 

 a reaction with a 90 per cent, solution of trichloracetic acid in 

 HC1, which gives red, then violet, then blue. 



Since all, or nearly all, cells contain cholesterin, it is perhaps 

 accumulated as one of the least soluble products of their 



1 Fischler, Cent. f. Path., 1904 (15), 913. 

 ^ieglei-'s Beitr., 1905 (7th suppl.), 343. 



3 Jour. Exp. Med., 1905 (7), 633. 



4 Wells, Jour. Med. Research, 1906 (14), 491. ^ 



5 Concerning the chemistry of cholesterin see introductory chapter. 



6 See Bostroem, Cent. f. Path., 1897 (8), 1. 



7 Pharm. Centralhalle, 1902 (43), 357. 



