1885.J 



Fat in the Liver- Cells of the Frog. 



235 



Sometimes the globules stretch, throughout the cells. In December, 

 the fat-globules may be more numerous in the outer part of the cells, 

 but more commonly they are absent from the outer cell-region and 

 form an inner zone. At other times of the year also, the fat-globules 

 may be present in the outer portion of the cells, but this is com- 

 paratively rare. 



From April to November, including those months, the globules 

 may be very few and small. In December this is, so far as I have 

 observed, very rare. In January, February, and March, I have 

 always found fat-globules to be present in considerable number. 



Effect of Temperature. — In December, when the fat in the liver is 

 increasing in amount, cold increases the amount of fat stored up, and 

 warmth decreases it. 



The increase of fat, consequent on a decrease of temperature, 

 occurs chiefly in the outer part of the cells. The fat-globules which 

 are formed are fairly large. 



The decrease of fat, consequent on increase of temperature, occurs 

 chiefly or wholly at the outer part of the cells ; as a rule, the number 

 of globules in the inner part of the cells is increased. The decrease 

 in the amount of fat, whilst due in part to a decrease in the number 

 of fat-globules, is due to a still greater degree to their decrease in 

 size. 



Although warmth lessens the amount of fat in the liver in winter- 

 frogs, it does not cause the fat to disappear entirely. The effect 

 varies ; in some frogs which have been kept seven to ten days at 

 22° C, the liver may still have considerably more fat than is ordinarily 

 present in the liver in summer-frogs. 



In summer-frogs, in which the fat-globules form an inner zone, and 

 are nearly or entirely absent from the outer cell-region, neither 

 warmth nor cold affects to any great degree the number or position 

 of the fat-globules. They usually diminish somewhat in number and 

 size with increase of temperature, but this is not necessarily the case. 

 Variations of temperature have then much greater effect on the 

 amount of fat in the liver in winter than in summer, i.e., whilst 

 in winter the ratio of fat formed to fat metabolised is greater 

 in the cold than in the warm, in summer this is not necessarily 

 the case. 



Although summer-frogs have sometimes very little fat in the liver, 

 it is doubtful whether the smallness of the amount is due either to 

 the warmth of summer or to hunger, for we have seen that warmth does 

 not necessarily cause a disappearance of fat from the liver; and frogs 

 after long hunger have not infrequently a fair amount of liver-fat left. 

 Hence the ratio of fat formed to fat metabolised, depends in part upon 

 certain unknown conditions of the body, independent of temperature 

 or of food. 



