306 



Messrs. W. Cramer and J. Lochhead. 



[Jan. 16, 



the " sparing " of the protein metabolism takes place only with a restricted 

 food supply, but that with an unrestricted supply of food the animals simply 

 take in more food and thus cover the requirements of the tumour. But the 

 experiments of Medigreceanu (4), which we are able to confirm from our own 

 observations, have shown that, even with an unrestricted food supply, tumour- 

 bearing animals do not eat more than normal animals. He also found that 

 the growth of the tumour, while it does not stimulate the host to an increased 

 intake of food, leads to an increase in the weight of the liver (5). It is 

 interesting to note that the same holds good also for pregnant animals. 



The sjDaring action on the protein metabolism referred to above might be 

 explained simply by assuming that in tumour-bearing rats more carbohydrate 

 material is burnt up instead of protein material, and that the glycogen which 

 disappears so rapidly from the liver of tumour-bearing animals, by being used 

 as a source of energy, protects an isodynamic equivalent of protein material, 

 which then becomes available for the foi'mation of new protoplasm. In that case 

 the part taken by carbohydrates would not be specific and could be taken equally 

 well by fats. On the other hand there is the possibility that the more rapid 

 disappearance of glycogen from the liver is due to the fact that, in addition 

 to the carbohydrate material which is burnt up and used as a source of 

 energy some glvcogen is used together with nitrogenous substances as 

 material for the synthesis of new protoplasm. 



The results of the observations on gaseous metabolism by Cramer and by 

 Chisholm indicate that the latter alternative is the correct one. For if in 

 tumour-bearing animals more carbohydrate were oxidised in place of proteins 

 than in normal animals, one would expect to find that the rise of the 

 respiratory quotient from about - 7 to about 1 which takes place after a meal 

 rich in carbohydrates should be more persistent in tumour-bearing animals 

 than in normal animals. But the observations which we have quoted show 

 that this is not the case ; on the contrary, if there is any difference between 

 tumour-bearing animals and normal animals it tends, in the case of rats, to be 

 in the direction of a less persistent rise of the respiratory quotient in the 

 tumour-bearing animals. 



We have repeatedly pointed out the close analogy which exists between the 

 metabolic conditions of pregnancy and those of an animal bearing a trans- 

 planted new growth. In the former, where a definite organ — -the placenta — 

 presides over the nutrition of the fetus, we have been able to show that 

 carbohydrates are used as a material for the building up of the foetal 

 protoplasm. The relation of the liver to the nutrition of the tumour is not 

 so intimate as that of the placenta to the nutrition of the foetus and does not 

 afford so direct an insight into this aspect of the problem. But the evidence 



