330 INFLUENCE OF HYPOPHYSIS-FEEDING ON SIZE 



considerable vigor. This condition may be taken as an indication 

 that the hypophysis-fed animal will finally reach a size much in excess 

 orf the size of the liver-fed animals. The same result was obtained 

 in two other experiments. 



The liver diet not only permits a higher rate of growth than that 

 resulting from an earthworm diet, but produces as high a rate of 

 growth as that caused by anterior lobe-feeding. There is, however, 

 an important difference between the effects of liver and hypophysis. 

 The liver-fed animals stop growing a short while after liver-feeding be- 

 gins, while the hypophysis-fed animals continue to grow at a high 

 rate. That age and size have nothing to do with this difference, is 

 clearly demonstrated by the fact that the hypophysis-fed male No. 

 3 of Experiment 2 is nearly as large (see Fig. 8) and just as old as the 

 liver-fed male of the same experiment. The same result was obtained 

 in two other experiments. 



An inspection of the photographs shows that the liver-fed animals 

 not only grow larger than the worm-fed animals, but exceed the 

 known maximum size of normal animals of the species. This is the 

 case with -the liver-fed male. No. 1, of Experiment 2 (Fig. 8), which 

 is 4.7 per cent larger than the largest known normal animal. It seems, 

 however, that liver does not permit growth beyond a certain size far 

 below that which hypophysis-fed animals attain. 



SUMMARY. 



1. Animals of the species Ambystoma tigrinuni when fed anterior 

 lobe can reach a size far in excess of that of animals fed earthworms 

 and presumably also of that of liver-fed animals. 



2. Liver produces a rate of growth as high as that resulting from 

 anterior lobe-feeding, but maintains growth only, until the animals 

 reach a definite size far below that of anterior lobe-fed animals. 



