ENDOGENOUS CATABOLISM 



15 



protoplasm is more readily decomposed than that of 

 mammals. 



Both explanations have some facts in their favor. In 

 starving animals, different organs suffer in different 

 degrees; the heart does not lose weight at all (Bayliss 

 p. 274), and seems able to use part of the catabolic 

 products from other tissues. Creatine appears in the 

 urine during complete starvation. It disappears, i.e., it 

 is re-utilized when carbohydrates are given, but not 

 when fats are given. The carbohydrates enable a 

 synthesis which retains the creatine in the body. 



With yeasts, we need not consider different tissues. 

 All cells are alike physiologically, and what has been 

 excreted as useless waste by one cell cannot be utilized 

 by any other cell of that same culture. 



Table 3. — ^Loss op Nitrogen by 5 Gm. op Yeast at 28°C. 



Rubner (1913) believed that endogenous catabolism 

 of yeast goes parallel with the rate of fermentation. He 

 gives some data on the loss of nitrogen by yeast in water 

 and sugar solution, and in two of the three experiments, 

 the loss in water is larger. But they were not carried 

 out with pure cultures; there was putrefaction in the 

 culture without sugar, i.e., a synthesis of bacterial pro- 

 toplasm from yeast excretions. This makes the experi- 

 ment quite doubtful. 



