20 THE VITAMINES 



proteins. That is to imply that the animal organism needs a smaller 

 amount of animal protein to maintain its nitrogen balance. This 

 view was utilized by Thomas (1) to group the various proteins of 

 animal and plant origin according to their biological value. All 

 these questions have exerted their influence upon the development 

 of the study of the vitamines, and are even now closely related to 

 many of our problems to which we shall call attention later. 



Another matter that is of interest, is the extent of the ability of 

 the animal body to synthesize many of the substances necessary for 

 its existence. The peculiar deficiency symptoms, of which we speak 

 in this book, have often been attributed to the apparent inability of 

 animals to synthesize some of the body constituents. The sub- 

 stances which, of all others, come to mind here are the nucleins and 

 the lipoids or phosphatides. If this were really the case, then these 

 substances would also have to be regarded as vitamines, a conception 

 which is upheld even now by some authors. The older animal 

 experiments, conducted with purified food substances, showed that 

 nucleins and lipoids actually could be synthesized. In spite of this, 

 we encounter in the work of the last ten years, the observation that 

 these substances have exhibited real therapeutic and nutritive 

 qualities, an observation that found its chief exponent in H. 

 Schaumann (2) who elaborated the theory of phosphorus insuffi- 

 ciency as an explanation of beriberi and similar diseases. This inter- 

 pretation was vigorously opposed by the writer and gave him the 

 chance to propound the theory of the vitamines. We shall speak of 

 the nucleins and lipoids in greater detail in another chapter, but we 

 shall also touch upon them lightly at this point. 



Even before the vitamines were known, reports were published 

 dealing with the synthesis of lipoids in the body. McCollum, 

 Halpin and Drescher (3) working with chickens on a lipoid-free 

 diet, showed that the eggs contained a normal amount of lecithin. 

 Fingerling (4) and also Abderhalden (5) were able to show that 

 animals could build up the needed organic phosphorus compounds 

 from inorganic phosphates. Still, we find in the description of the 

 condition of the above animals, some observations that point to the 

 necessity of lipoids for life. It remained for vitamine research to 

 clear up this matter completely. 



In this connection, we shall mention, first of all, the important 

 work of Stepp (6) in 1909. He made the significant observation that 



