690 VI. OCCURRENCE OF LIPIDS IN THE ANIMAL 



tract was not due to a stimulation of appetite, nor to the small choline con- 

 tent of the liver extract. 



(I) Summary of Factors Related to Fatty Livers. The factors which are 

 responsible for the production of fatty livers are numerous, but they fall 

 into a limited number of categories, viz: (A) Conditions in which fat 

 becomes the chief source of calories, as in starvation or carbohydrate 

 deprivation, due either to lack of carbohydrate in the diet or to failure to 

 utilize it, as is the case in diabetes (physiologic fatty liver) ; (B) conditions 

 involving the failure of fat transport and utilization due to dietary de- 

 ficiencies which prevent lecithin synthesis (1 ,2) ; (C) conditions involving 

 the prevention of fat transport and utilization by removal of components 

 essential for lecithin synthesis with competing reactions {6,7,8,9,11,12); 

 (D) conditions involving an increased requirement for lipotropic agents 

 (8,10); and (E) conditions causing an increased mobilization of fat 

 (13,1 If). Table 25 summarizes the causes for the several types of fatty 

 livers and the effect of lipotropic agents in combatting them (page 688). 



d. The Effect of Fatty Livers on the Functioning of the Liver. One 

 might expect that a difference in metabolism would obtain between the 

 dietary type of fatty livers and those resulting from injury to the hepatic 

 tissue. It appears highly probable that abnormalities in metabolism may 

 occur when the fatty liver has resulted from liver poisons involving an in- 

 jury to the cell structure. However, it is less certain that a metabolic up- 

 set would result in the animal having the dietary type of fatty liver; in this 

 latter condition, the cells remain intact, although they are engorged with 

 fat. However, it will be observed that a derangement occurs in a number 

 of hepatic functions, even when this latter type of fatty infiltration of the 

 liver is present. 



(a) Metabolic Changes Occurring in Animals Having Fatty Livers Pro- 

 duced by Hepatic Poisons. Although profound changes occur almost im- 

 mediately in animals subjected to hepatectomy, and death ensues within a 

 limited time interval, the presence of even small amounts of functioning 

 liver tissue will prevent such difficulties. Thus, although urea synthesis 

 was completely inhibited and blood amino nitrogen consequently increased 

 proportionally in dogs 896 and monkeys 897 following the excision of the liver, 

 McMaster and Drury 898 reported that these reactions were not appreci- 

 ably impaired until 90% of the liver had been removed. Moreover, 



896 J. L. Bollman, F. C. Mann, and T. B. Magath, Am. J. Physiol., 69, 371-392 (1924). 



897 S. Maddock and A. Svedberg, Am. J. Physiol, 121, 203-208 (1938). 



898 P. D. McMaster and D. R. Drury, J. Exptl. Med., 49, 745-758 (1929). 



