NUTRITION. 303 



the experimental methods which we have developed are proving useful 

 to other investigators in connection with their studies in related fields. 



In view of the extraordinary effects observed in our earlier experi- 

 ments, when vitamines were removed from or added to otherwise 

 adequate diets, we have been largely occupied during the current year 

 with experiments to determine the distribution and relative proportion 

 of these essential factors in various animal and vegetable foods. This 

 seemed important, as information in this field has been very scanty 

 and practically none of it has been of a quantitative character. 



We have undertaken to determine the minimal amounts of the 

 following animal tissues which furnish sufficient water-soluble vitamine 

 for the growth of rats: skeletal muscle, heart muscle, liver, kidney, 

 brain, and pancreas. Thus far we have learned that skeletal muscle 

 (round of beef) furnishes so little of this vitamine that meat must be 

 counted on as a minor source of this food factor in the human dietary. 

 On the other hand, the heart muscle is richer in water-soluble vitamine 

 and appears to contain not a Httle of the fat-soluble. Liver and 

 kidney likewise contain both of these vitamines in comparatively 

 considerable quantities, while brain tissue contains less of the water- 

 soluble \'itamine than any of the above animal tissues except skeletal 

 muscle. As to the fat-soluble vitamine in brain or either vitamine 

 in the pancreas, we are not yet prepared to make definite statements. 

 Incidentally we have established that each of these animal tissues, 

 except the pancreas, contains protein adequate for normal growth. 

 Experiments with pancreas are not yet complete. 



Of animal products, milk has been studied in respect to the relative 

 quantity actually required to furnish enough water-soluble vitamine 

 for growth, and also the effect of heating and other treatments on this 

 vitamine. Comparison was made between fresh untreated milk, 

 pasteurized milk, our so-called ''protein-free milk," and a commercial 

 milk powder. Equivalent amounts of each of these were equally 

 effective in promoting normal growth, hence the water-soluble vitamine 

 is apparently not damaged by the processes employed in making our 

 protein-free milk, the commercial milk powder, or in pasteurizing milk. 



In our experiments much larger quantities of milk were required to 

 furnish enough vitamine for normal growth than is generally supposed 

 to be sufficient. Thus when 12 per cent of milk powder or equivalent 

 amounts of fresh milk or "protein-free milk" were fed, young animals 

 grew Httle, if at all, although the diet was in other respects wholly 

 adequate. When this quantity was doubled growth was approximately 

 normal. Even the daily separate feeding of 16 c. c. of fresh milk, the 

 solids of which were equivalent to about 25 to 30 per cent of the 

 average amount of food eaten, rarely caused satisfactory growth, and 

 even in the most successful experiments better growth was made 

 when a little yeast was also given. Compared with dried brewer's 

 yeast, or wheat embr}''o, of either of which 1.4 grams per week fur- 



