130 



TEXT-BOOK OF PHYSIOLOGY 



The results of an analysis of the organs and tissues of a cat after a thirteen- 

 day period of starvation, during which the animal lost 1017 grams in weight, 

 are given in the following table, based on data furnished by Voit: 



It will be observed from this table that the adipose tissue suffers the 

 greatest loss, the entire amount disappearing with the exception of a small 

 portion in the posterior part of the orbital cavity and around the kidneys. 

 The muscles, though losing only 31 per cent, of their weight, yet furnish 

 429 grams of presumably protein material, for nutritive purposes. The 

 heart and nervous system experience but slight loss. 



Mixed Diet. The chemic composition of the tissues, taken in con- 

 nection with their metabolism during starvation, implies that no one article 

 of food is sufficient for tissue repair and heat production; but that all classes 

 of foods in other words, a mixed diet are essential to the maintenance of 

 a normal nutrition. Experimental investigation has also conclusively 

 established this fact. Moreover, the amounts of nitrogen and carbon elimi- 

 nated daily, and the ratio existing between them, indicate the amounts 

 of protein, fat, and carbohydrate which are required to cover the loss. 



Metabolism on a Purely Protein Diet. Notwithstanding the chemic 

 composition of the proteins and the possibility of their giving rise to either 

 fat or a carbohydrate during their metabolism it has been found extremely 

 difficult to maintain the normal nutrition for any length of time on a pure 

 protein or fat-free flesh diet. This, however, has been accomplished with 

 dogs. It was found, however, that, in order to maintain the nitrogen equi- 

 librium, it was necessary to increase the proteins from two to three times 

 the usual amount. Thus, a dog weighing 30 to 35 kilograms required from 

 1500 to 1800 grams of flesh daily in order to get the requisite amount of 

 carbon to prevent consumption of its own adipose tissue. Under similar cir- 

 cumstances, a human being weighing 70 kilograms would require more than 

 2000 grams of lean beef an amount which, from the nature of the digestive 

 apparatus, it would be practically impossible to digest and assimilate for any 

 length of time. Even the slight habitual excess beyond the amount normally 

 required is imperfectly assimilated and gives rise to the production of 

 nitrogen-holding compounds which are more or less difficult of elimination. 



