FATTY METAMORPHOSIS 409 



Summary. — We must conclude, tiierofore, 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 apf)arent 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. 



Pathogenesis 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 con- 

 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 applying the 

 commonlj' accepted ideas concerning fat metabolism, a satisfactory 

 explanation seems to be possible. Fat is always utilized and trans- 

 ported in the form of its two constituents, fatty acid (or soaps) and 

 glycerol, which are diffusible and soluble. It enters and leaves the 

 cells in this condition, being split or combined, as may be necessary to 

 produce equihbrium, by the action of lipase, which is present within 

 the cells and in the blood and lymph. Under normal conditions there 

 is little free visible fat in the cells of the parenchymatous organs, 

 because it is largely used up through oxidation of the glycerol and 

 fatty acids by the action of the intracellular oxidases, ^yhe^e there 

 is abundant lipase and but little oxidative activity, as is the case in 

 the areolar fat tissue, fat accumulates in large amounts. When, for 

 any reason, the oxidative power of the parenchymatous organs is re- 

 duced, fat accumulates in them as it does in the fat depots normally, 

 and we have an excess of fat in the parenchymatous cells; thus, in 

 pubnonary tuberculosis, severe or protracted anemias, etc., a great 

 accumulation of fat occurs, particularly in the Kver, where normally 

 active oxidative processes continually balance the action of the abun- 

 dant Hpase of the liver-cells. The liver being normally concerned in 

 the preparation of fat for metabolism, it is also perfectly possible to 



