80 FEEDING EXPERIMENTS WITH ISOLATED FOOD-SUBSTANCES. 



The preparation apparently contains a small excess of iron over 

 that found in cow's milk probably as a contamination from the 

 desiccating process used. It is obtainable in easily manipulated form 

 and with the addition of a small amount of nitrogen-free lard and 

 starch forms a food paste readily consumed by rats. These pastes 

 have been used, either with or without our earlier standard salt 

 mixture (I),* as follows: 



"Trumilk" 



Starch 



Lard 



Salt mixture I 



Nitrogen content. 



We have carried rats through the period of growth as well as 

 pregnancy on this diet alone, from the time that they were removed 

 from the mother (cf. Charts XXXI, XXXII, and XXXIII). 



As a further illustration of the excellent nutritive properties and 

 physiologically appropriate ' ' combination ' ' of food ingredients in the 

 milk food-mixture, illustrative charts are appended to show the re- 

 covery of rats moribund after prolonged periods of malnutrition, with 

 lack of inorganic salts in the dietary (Charts XXXIV and XXXV). 

 Many similar illustrations might be reproduced, giving evidence of 

 the perfect realimentation of rats by the use of the milk food (cf. 

 Charts XXVIII, LXV, XCIX, and C). 



Remembering that our earlier trials with casein, the chief protein 

 ingredient of the milk powder, and with combinations of casein and 

 other proteins were at best successful only in maintaining nutritive 

 equilibrium and that not indefinitely and were never adequate 

 for the manifestation of real growth, we directed our attention to the 

 non-protein constituents of milk. After numerous failures to modify 

 the inorganic and non-protein ingredients of our dietaries by altering 

 the relation of proportions of the various ions as well as the character 

 of the carbohydrates and fats, it occurred to us that the protein-free 

 portion of the milk might give the clue to the successful feeding of pro- 

 teins which did not appear to be the inefficient factors in our cases of 

 malnutrition. Accordingly a product was prepared as follows: 



Perfectly fresh centrifugated milk, nearly free from fat, was pre- 

 cipitated in lots of about 36 liters by diluting with 7 liters of distilled 



*This mixture, prepared in imitation of Rohmann's successful product and empirically 

 found by use to be the most satisfactory of the different combinations tried, has the 

 following composition: 



Grams. Grams. 



Ca3(P04)2 10.0 Mg citrate 8.0 



K2HPO4 37.0 Ca lactate 8.0 



NaCl 20.0 Fe citrate 2.0 



Na citrate 150 



100. o 



(Cf. our previous report, Feeding experiments with isolated food-substances, Publi- 

 cation No. 156, Carnegie Institution of Washington, p. 1,2.) 



