358 CARNEGIE INSTITUTION OF WASHINGTON. 



case it was found that weight for weight the mature hay was much less 

 efficient as a source of water-soluble vitamine than was the immature 

 plant. If it should be proved that the vitamine content of milk is 

 influenced by the vitamine content of the ration of the dairy cow, it is 

 quite possible that proportion of vitamine in milk could be increased by 

 feeding hay made from young, immature plants instead of that made 

 from the more mature ones. Inasmuch as milk has been found to be 

 somewhat less rich in the water-soluble vitamine than was supposed 

 at one time, it would be a great advantage if some means could be 

 found for increasing its content in this food accessory, especially for the 

 sake of children and invalids, who quite possibly not infrequently suffer 

 from an insufficient supply of this unidentified essential. 



Our experiments, as well as those of other investigators, have shown 

 that animals require a supply of the water-soluble vitamine throughout 

 their entire lifetime. Whether or not the need for the fat-soluble 

 vitamine is also manifested during the complete life cycle or only during 

 certain periods is still an unsolved question. To investigate this, a 

 number of fully mature animals were fed rations supposedly free from 

 this food accessory and on which young rats inevitably would cease to 

 grow and would decline in weight after about three months. Some of 

 these adult animals have received such diets exclusively for nearly a 

 year without manifesting any of the obvious symptoms characteristic 

 of animals fed on a diet deficient in this vitamine. Whether or not 

 these animals have suffered disturbances in their metabolic processes 

 has not been determined. In this connection we recall the incidence of 

 urinary calculi among rats fed on diets deficient in fat-soluble vita- 

 mine already i-ef erred to in an earlier report. Another series of animals 

 which had received limited quantities of the fat-soluble vitamine during 

 the early part of their growing period was deprived of this food acces- 

 sory just before they had reached full maturity. These were well 

 maintained, and some even grew considerably during the next six 

 months; but eventually they declined suddenly in weight, and were 

 then brought back to a condition of normal nutrition by the adminis- 

 tration of butter fat, or some other source of the fat-soluble vitamine, 

 without any other change in the food. Apparently adults do not need 

 so abundant a supply of fat-soluble vitamine as do growing animals, 

 but our experiments have not yet justified final conclusions in respect 

 to this important problem. If the results of our still incomplete experi- 

 ments can be applied to human nutrition, it would seem that adults 

 need less fat-soluble vitamine than do growing children in order to 

 avert nutritive disaster, but, in view of our present limited knowledge 

 of this subject, the fat-soluble vitamine should not be eliminated 

 entirely from the dietary of adults. 



Inasmuch as we have used yeast extensively as a source of water- 

 soluble vitamine in our nutrition experiments, and particularly in 



