406 RETROGRESSIVE CHANGES 



has been able to stain the lipoids in the normal kidney and other tis- 

 sues, in sufficient amount to account for all the so-called "masked 

 fat," which thus seems to be, as also indicated by chemical evidence, 

 largely lipoidal. 



Jastrowitz -^'^ has studied the relation of lipoids to fats in the fatty 

 changes produced by various means, and finds that in severe fatty 

 changes with much transported fats there may be little change in the 

 lipoids; with blood poisons which cause little increase in total fats, 

 the lipoid content of both blood and organs may be high ; usually the 

 phosphatid content is unchanged or slightly increased, but it may be 

 decreased. The proportion of cholesterol to neutral fats is usually 

 within normal limits in tissues showing fatty changes.-*^ The mito- 

 chondria seem to be compounds of phospholipins with proteins, and 

 these agglutinate and form fatlike droplets in phosphorus poison- 

 ing ; -^'^ presumably they play an important role in fatty metamor- 

 phosis. 



Summary. — We must conclude, therefore, that fatty degeneration 

 of an organ means, in the case of the liver, myocardium, and pan- 

 creas, an infiltration of neutral fat from outside into cells which have 

 been degenerated by the action of poisons or other injurious influ- 

 ences, plus a certain amount of apparent increase in fat because of the 

 setting free of previously invisible fats and lipoids normally present 

 in the affected cells. In the kidney, spleen, and muscles an increase 

 of fat seldom occurs from these causes, but the cells may show a 

 marked fatty metamorphosis through the setting free of the invisible 

 intracellular fat and lipoids by autolytic or physico-chemical changes. 

 In the adrenal, kidney, and often in other tissues, the fatty material 

 present in the cells is characterized by being doubly refractile, and 

 then consists chiefly of cholesterol esters, together with greater or less 

 quantities of phosphatids, fatty acids, soaps and neutral fats. 



CAUSES OF FATTY METAMORPHOSIS 



Nevertheless, the old anatomical distinction of infiltration and de- 

 generation still remains, provided we do not hold to the original idea 

 that the term degeneration implies that the cell protein has been eon- 

 verted into fat ; for we must recognize that under some conditions the 

 cells may take up great quantities of fat without suffering any appre- 

 ciable degenerative changes, whereas in other instances the appear- 

 ance of fat is associated with marked and complete disintegration of 

 both nucleus and cytoplasm. Furthermore, we have yet to explain 

 why, under some conditions, the fat is removed from the fat depots 

 to be stored up in the liver or other organs. By appl.ving the com- 

 monly accepted ideas concerning fat metabolism, a satisfactory ex- 



28aZeit. exp. Palli. u. Tlior., 1914 (15), 110. 

 28bCzyhlarz and Fudis, Biochem. Zeit., ]!)14 (63), 1.31. 

 28c Scott, Amer. Jour. Anat., 1916 (20), 237. 



