NUTRITION. 359 



test diets in which the presence or absence of the fat-soluble vitamine 

 was under investigation, it became essential to ascertain conclusively 

 whether the yeast was also perchance contributing some of the fat- 

 soluble component. Having demonstrated that dried brewery yeast 

 is an adequate source for the protein and water-soluble vitamine 

 needed during growth, we fed young rats upon a diet consisting of 

 dried yeast, starch, a salt mixture, and lard. They made a little 

 growth and began to decline in weight after 51 to 72 days; but growth 

 was promptly renewed when butter fat was added to the ration. Inas- 

 much as the diet contained 42.5 per cent of yeast, it seems to be con- 

 clusively shown that the few centigrams of yeast commonly added as a 

 source of water-soluble vitamine to our mixtures of isolated food sub- 

 stances can not be the carrier of significant amounts of the fat-soluble 

 vitamine. This is in accord with the recently published conclusions 

 of Drummond. 



In preparing food materials as free as possible from all traces of fat- 

 soluble vitamine by extraction with boiling absolute alcohol, the yeast 

 was subjected to a similar treatment. Special tests which have been 

 conducted with this extracted product in combination with a vitamine- 

 free diet have shown that the water-soluble vitamine is not lost by the 

 mode of treatment indicated. 



The question has been raised as to the possible destructive influence 

 of the high temperatures employed in the canning industry. To test 

 this point, samples of washed meat residue and yeast were heated at 

 about 20 pounds pressure for an hour. The rats fed on rations con- 

 taining the pressure-cooked meat residue grew just as well as those 

 which received the ordinary preparation of meat residue, showing that 

 the long cooking apparently had no unfavorable influence on the value 

 of the protein. The pressure-cooked yeast, although it was by no 

 means inactive, proved to be somewhat inferior to the uncooked yeast 

 as a source of water-soluble vitamine, showing that heating for an 

 hour at high temperatures tends to destroy the water-soluble vitamine. 

 In practice, however, few, if any, of the canned products are subjected 

 to such a high temperature for so long a time as were these, so that it is 

 probable that under ordinary circumstances the water-soluhle vitamine 

 in canned goods is not seriously damaged. This statement does not 

 apply to the anti-scorbutic potency of foods. 



That the water-soluble vitamine is not destroyed by long storage 

 is shown by the fact that yeast, protein-free milk, and various vege- 

 table products which have been kept for a year or longer have shown 

 no appreciable diminution in their vitamine potency. 



One well-grounded objection to the experiments made in the past 

 to determine the nutritive value of the individual proteins in the pure 

 state has been founded on the fact that in furnishing the vitamine 

 necessary to the animal's existence not inappreciable quantities of 



