FATTY METAMORPHOSIS 403 



hartlly be questioned.'* "Fatty degeneration/' tliercforc, at least in 

 some cases, differs from "fatty infiltration" chiefly in the fact that 

 in the former the process is associated with serious injury to the cell, 

 caused by the action of toxins or loss of nutrition, while in the latter 

 the cell is not seriously injured and is capable of returning to its nor- 

 mal condition whenever the fat is removed. '■* 



Fatty "Degeneration" without Infiltration. — By showing 

 that new fat in fatty livers is infiltrated fat, Rosonfeld did not entirely 

 clear up the subject, for, in the course of his analyses of organs that 

 were micro- or macro-scopically the seat of fatty degeneration, he 

 found that there is not always any correspondence between the amount 

 of fat that seems to be present, as determined by microscopic methods, 

 and the amount that chemical analysis shows to be present. This 

 is particularly true of the kidney. Thus, the amount of fat and 

 lipoids, or lipins, present in normal kidneys (dog) was found to vary 

 between 18.5 per cent, and 29.12 per cent, of the dry weight, the aver- 

 age being 21.8 per cent.; whereas, after producing a typical "fatty 

 degeneration" by means of phosphorus and other poisons, the lipin 

 content was still found to be between 16.9 per cent, and 22.6 per cent.^" 

 In all instances the amount of lipins in kidneys showing typical fatty 

 degeneration under the microscope was found equal to or less than 

 the normal amount — it was never increased. The same conditions 

 were found to obtain in human kidneys that showed fatty metamor- 

 phosis. Microscopic examination of specimens stained with the speci- 

 fic fat stains,'' therefore, gives no indication of the amount of fat 



8 Schwalbe (Verh. der Deut. Path. Gesell., 1903 (6), 71) claims that in a sim- 

 ilar way iodin compounds of fat can be demonstrated to be transported into the 

 fatty organs. His analyses were merely qualitative and by quantitative deter- 

 minations 1 was unable to corroborate his conclusions (Zeit. f. physiol. Chem., 

 1905 (45), 412). 



^ A striking proof of the lack of injury associated with fatty infiltration is 

 shown by the fatty infiltration frequently seen in the liver, especially of alcoholics, 

 in which it may be difficult to find, microscopicallj', anj' cell cytoplasm because 

 of the fat, the tissue looking like fatty areolar tissue; and j^et there may be no 

 clinical evidence whatever that the liver fimotion has been impaired by the process. 



1" Concerning the normal intracellular fats see introductory- chapter. 



" Fat-staining involves several principles of interest in this connection. (See 

 reviews by BuUard, Jour. Med. Res., 1912 (27), 55 and Escher, Corrlil. Schweizer 

 Aertze, 1919 (49), 1609.) Osmic acid (OsO^), the longest used for this purpose, is 

 reduced to OsOi by oleic acid, imparting a black or dark-brown color to the fat; 

 but it does not stain staurated fatty acids, such as palmitic or stearic acid. Thus, 

 Christian found in pneumonic exudates fat that stained by other methods but not 

 by osmic acid, apparently because it contained no oleic acid (Jour. Med. Research, 

 1903 (10), 109). Sudan 111 and scarlet II {fat inmccau) are two sj-nthetic dyes 

 which stain fat in a purely physical way, entering and remaining in the fat-droplets 

 because they are much more soluble in fat than they are in water or alcohol. 

 (Fulh^ discussed by Michaelis (who introduced scarlet R) in Virchow's Arch., 1901 

 (164), 263; and by Mann, "Physiological Histology," p. 306.) These stains have 

 the advantage of staining all sorts of fats and not staining other substances that 

 may reduce osmic acid. Fatty acids and soaps may be stained with copper acetate, 

 which forms a green copper salt, and thus be distinguished from fats (Benda, Vir- 

 chow's Arch., 1900 (161), 194). J. Lorrain Smith (Jour. Path, and Bact., 1907 

 (12), 1) has introduced as a fat dye, Nile blue sulphate, which forms a blue salt 

 with free fatty acids, while neutral fats are stained red bj' the oxazone base. 



