CAUSES bl- FATTY M iriA MOh'l'HOSIS 407 



planation 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 equilibrium, 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 througli oxidation of the glycerol and 

 fatty acids by the action of the intracellular oxidases. AVhere there 

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

 the areolar fat tissue, fat accumulates in large amounts. AVhen, 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 

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

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

 active oxidative processes continually balance the action of the abun- 

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

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

 have an accumulation of fat in the nonnal liver merely as a result of 

 increased function, and hence fatty changes may be purely physio- 

 logical in this organ. "^^ 



If the fat accumulates in cells that are structurally normal or 

 nearly so, the fat-droplets fuse together under the pressure of the 

 c\i:oplasm, and w^e get the picture of a typical fatty infiltration; in- 

 deed, the only tissues in which we get this typical infiltration are the 

 liver and the fatty areolar tissue, in both of which the process is pre- 

 sumably physiological in character even if not always physiological 

 in degree. If the cells are much disintegrated through the action of 

 the poison, — e. g., phosphorus, bacterial toxins, etc., — the accumulat- 

 ing fat-droplets are not crowded into one large droplet, but lie free 

 in the granular debris of the disintegrating cell, constituting the typi- 

 cal appearance of fatty degeneration. Fatty degeneration is usually 

 brought about by poisons, while abnormal fatty infiltration depends 

 usually upon decreased oxidation, due to lack of either oxygen or 

 hemoglobin in the blood. If the anemia is extreme, however, the cells 

 degenerate, and then we find a true fatty degeneration caused by lack 

 of oxygen.^" Thus, in an anemic infarct fat accumulates about the 

 periphery of the dead area,^^ probably because fatty acids and glycerol 

 diffuse in slowly from the surrounding parts where circulation still 



29a See Coope and Mottram, Jour, of Phvsiol., 1914 (40), 23; Ilellv, Beitr. path. 

 Anat... 1914 (00), 1. 



"io Mohr (Zeit. exp. Path., 1906 (2), 434) denies that oxidation is decreased in 

 anemia; and in a man with but about half the normal lunw area the metabolism 

 was not found altered to anv extent bv Carpenter and Benedict, Amer. Jour. 

 Phvsiol., 1909 (23), 412. 



siFischler, Cent. f. Path., 1902 (13), 417. 



