FEEDING EXPERIMENTS WITH ISOLATED FOOD SUBSTANCES. 



43 



190 



170 



150 



0.05 



-0.10 



20 



100 



Days 

 Chart XVI. Rat 25 fed 176 days on pure Casein as the only protein, Diet 4, p. 33. 



These experiments, with rats 23, 24 and 25, extending over 135-160 

 days without noteworthy alterations in the weight and with a very large 

 gain of nitrogen, are, as far as we are aware, the most successful recorded 

 attempts at artificial nutrition with a constant mixture of pure food- 

 stuffs including a single protein. 



CASEIN AND VEGETABLE PROTEIN DIET. 



Without reporting here the numerous trials and failures to 

 replace part or all of the casein by other proteins, a few data from 

 our records may throw light upon the difficulties thus encountered. 

 The proportion of the nutrients is the same in these experiments, one- 

 third or more of the casein being replaced by the proteins indicated. 



A casual inspection of the succeeding pages shows that the 

 failure to eat is frequently sufficient to account for the failure to 

 maintain body-weight and tissue. The animals lost weight to the 

 extent of their fat content and then speedily succumbed with indi- 

 cations of inanition rather than any specific pathological metabolism. 

 Those rats which ate less than 40 grams of the mixed food were 

 unable to maintain their nutritive equilibrium. A further evidence 

 that no permanent defect is induced by the character of the diet is 

 found in the observation that a change to a mixed diet of seeds and 

 vegetables often brought speedy realimentation and recovery. 



