MAINTENANCE REQUIREMENTS OF MATTER 349 



rise to the disease. Aqueous extracts of other substances, 

 notably yeast, are capable of producing the same curative effects. 

 The substances themselves have not yet been isolated but 

 Funk, 1 who has been prominent in this line of investigation, 

 has given them the general name of vitamins. It is thought 

 that other nutritional diseases, such as scurvy and pellagra, 

 as well as the cotton-seed poisoning of swine, are likewise due 

 to the use of diets deficient in these vitamins. 



438. Growth substances. Very interesting facts of a some- 

 what similar character have been observed regarding growth, 

 notably by Hart and McCollum, and by Osborne and Mendel. It 

 seems to have been demonstrated that there are associated with 

 certain fats, such as butter fat, the fat of egg yolks, cod liver 

 oil, etc., substances whose absence from a ration otherwise 

 adequate renders it incapable of permanently supporting 

 growth. That this substance (or substances) differs from the 

 vitamins of Funk seems apparent from the fact that normal 

 maintenance may apparently be secured on rations from which 

 it is absent. 



The very interesting results obtained by Hart, McCollum, 

 Steenbock and Humphrey 2 with cows fed rations properly 

 balanced according to the ordinary criteria but made up from 

 the products of single plants (wheat, oats, maize) suggest that 

 substances similar to the vitamins or the growth substances 

 may play an important part in the nutrition of farm animals. 

 These rations when continued for two or three years mani- 

 fested specific differences in nutritive effect as regards growth 

 and reproduction, although all of them seemed to be fairly ade- 

 quate for the maintenance of live weight. 



Most investigations upon these accessory substances, however, 

 have been directed to their relation to growth and further 

 discussion of their functions in nutrition may therefore be 

 deferred until that subject is considered. 



1 Ergeb. Physiol., 13 (1913), 125. 



2 Wis. Expt. Sta., Research Bui., No. 17 (1911). 



