198 PHYSIOLOGICAL CHEMISTRY 



ops beri-beri. A similar condition appears in chickens on a 

 rice diet, and extensive studies have been carried out to ascer- 

 tain the nature of the curative substance and of the disease. 

 Funk has called the unknown material "vitamine," a name to 

 which there are some objections, and believes that the substance 

 contains nitrogen. McCollum, and Osborne and Mendel recog- 

 nize two substances, one of them present in butter fat, and dif- 

 fering from the substance in rice polishings by containing no 

 nitrogen. The substance in butter fat appears to be essential 

 to growth. McCollum has adopted the terminology ''Fat Sol- 

 uble A" and "Water Soluble B" for the two materials. Al- 

 though much labor has been expended on the problem, the 

 chemical nature of these various important materials still is 

 unknown. A great variety of compounds have been studied, 

 and shown not to be the desired unknown. Undoubtedly the 

 problem will be solved in the not distant future. 



The investigation of these unknown, but essential dietary 

 constituents is made difficult by the fact that they are present 

 in the foods, and are required by the body in extremely minute 

 amounts, a few miligrams being sufficient to supply all the 

 body's daily needs. 



Various diseases other than beri-beri, such as scurvy and 

 pellagra, also have been considered by some to be due to lack 

 of some such unknown substances. They have been classed as 

 "deficiency diseases." Evidence is not conclusive on this point, 

 and it is perhaps wiser to await further developments before 

 drawing conclusions. Recent unpublished results of McCollum 

 seem to indicate that scurvy does not belong in this class. 



Fortunately, the unknown dietary substances are fairly widely 

 distributed in ordinary foodstuffs. Butter fat, milk, meat, 

 yeast, orange juice, fresh vegetables and other common articles 

 of diet contain one or more of the unknown substances which 

 the body needs. Just why the body needs these materials and 

 the functions which they perform are matters as yet obscure. 

 Possibly they stimulate or regulate the functioning of certain 

 tissues or cells, possibly they are used as materials for the con- 



