140 ANNUAL REPORT SMITHSONIAN INSTITUTION, 19 34 



produced in the anterior portion of the pituitary gland situated at 

 the base of the brain, which by circulating to the ovary controls the 

 succession of its hormonal activities. The cases I have mentioned 

 are far from exhausting the numerous hormonal influences now 

 recognized. 



For full appreciation of the extent to which chemical substances 

 control and coordinate events in the animal body by virtue of 

 their specific molecular structure, it is well not to separate too widely 

 in thought the functions of hormones from those of vitamins. 

 Together they form a large group of substances of which every 

 one exerts upon physiological events its own indispensable chemical 

 influence. 



Hormones are produced in the body itself, while vitamins must be 

 supplied in the diet. Such a distinction is, in general, justified. 

 We meet occasionally, however, an animal species able to dispense 

 with an external supply of this or that vitamin. Evidence shows, 

 however, that individuals of that species, unlike most animals, can 

 in the course of their metabolism synthesize for themselves the 

 vitamin in question. The vitamin then becomes a hormone. In 

 practice the distinction may be of great importance, but for an 

 understanding of metabolism the functions of these substances are 

 of more significance than their origin. 



The present activity of research in the field of vitamins is pro- 

 digious. The output of published papers dealing with original in- 

 vestigations in the field has reached nearly a thousand in a single 

 year. Each of the vitamins at present known is receiving the 

 attention of numerous observers in respect both of its chemical and 

 biological properties, and though many publications deal, of course, 

 with matters of detail, the accumulation of significant facts is growing 

 fast. 



It is clear that I can cover but little ground in any reference to 

 this wide field of knowledge. Some aspects of its development have 

 been interesting enough. The familiar circumstance that attention 

 was drawn to the existence of one vitamin (Bi so called) because 

 populations in the East took to eating milled rice instead of the 

 whole grain; the gradual growth of evidence which links the 

 physiological activities of another vitamin (D) with the influence of 

 solar radiation of the body, and has shown that they are thus 

 related, because rays of definite wave length convert an inactive 

 precurser into the active vitamin, alike when acting on foodstuffs 

 or on the surface of the living body; the fact again that the recent 

 isolation of vitamin C, and the accumulation of evidence for its 

 nature started from tlie observation that the cortex of the adrenal 

 gland displayed strongly reducing properties ; or yet again the proof 

 that a yellow pigment widely distributed among plants, while not 



