ISOLATED PROTEINS AND " PROTEIN-FREE " MILK. 83 



The results can be grouped in two series, viz : 



Diet = Isolated protein, protein-free milk, starch, agar, fat. 



The failures in group n lead to the conclusion that the proteins, 

 gliadin and hordein, are inadequate for the functions of growth. We 

 are presumably dealing with a chemical inadequacy rather than any 

 toxicity and consequent lack of growth, judging by the fact that the 

 gliadin and hordein rats are maintained in good, nutritive condition 

 even in the absence of growth . Their body-weight is scarcely changed 

 at all. Without the use of the protein-free milk or faeces-feeding 

 gliadin rats have usually declined (Charts XCVIII, XCIX, and C). 



A second reason why the success of these trials is not due to the 

 presence of possible minute contaminations with milk protein is 

 discoverable in Charts XLJII, XLJV, XTV, XLVIII, XLIX, L,, LI, 

 CVIII, CIX, CX, and CXI. Here the addition of not inconsiderable 

 portions (5 to 30 per cent) of the actual milk food to the earlier 

 inefficient protein mixtures is incapable of bringing about growth in 

 any degree equal to that at once initiated when the protein-free milk 

 is added in relative abundance. 



Further evidence that a trace of milk proteins is not responsible 

 for the growth of the rats fed with mixtures containing our protein- 

 free milk powder is furnished by experiments in which successively 

 larger quantities of the milk food are added to the gliadin food. Here 

 we see that growth gradually increases with the larger additions of 

 the milk food, although with even as much as 30 per cent in the food 

 the rate of growth is much below normal. With additions of 5 or 

 even 20 per cent of the milk food, the rate of growth is very slow, as 

 shown by Charts CIV, CV, CVI, and CVII. That this result is to be 

 attributed to the proteins introduced in the milk food and not to a 

 combination of a small quantity of milk proteins together with a 

 sufficient quantity of the inorganic or other constituents of the milk 

 is shown by experiments now in progress in which the addition of the 

 milk food to the gliadin and protein-free milk food is producing 

 normal growth. In this mixture we have all of the constituents of 



