HISTORICAL SURVEY 



In spite of the fact that the knowledge of the vitamines taken as 

 a whole is not older than ten years, and although until lately, the 

 idea was prevalent that for the complete nutrition of an animal 

 organism only proteins, fats, carbohydrates, salts and water were 

 necessary, there is nevertheless, in the older literature, no lack of 

 statements which of themselves should have given rise to an eager 

 search for additional dietary components essential to life. The 

 progress which has already been made by research in vitamines 

 removes all doubt as to the actual existence of such substances, and 

 every year brings forth new findings which enhance the importance 

 of the vitamines to life. 



The scientific research leading to the conception of the vitamines 

 proceeded through many intermediate stages, which we shall shortly 

 describe. A great stimulus to the development of the modern science 

 of nutrition was furnished by the investigations into the chemistry 

 of the proteins which we owe, above all, to the classical work of 

 Emil Fischer and Kossel. These investigations not only contributed 

 to the knowledge of the composition of the proteins, but also gave rise 

 to the study of the relationship between the individual dietary con- 

 stituents. They demonstrated particularly, that the various proteins 

 exhibited, qualitatively as well as quantitatively, a varied composi- 

 tion, and that naturally occurring proteins have not the same physi- 

 ological value. Without going into details, which may be found in 

 any text-book, we shall take up only those facts bearing upon the 

 study of the vitamines. It has been shown by many investigations 

 that certain amino acids, such as tyrosine, tryptophane, arginine and 

 lysine, are more or less indispensable to the animal organism. This 

 question is not yet completely settled, but we know, however, that 

 some proteins, for example, zein (which is lacking in tryptophane), 

 or gelatine (which lacks several important amino acids), are not 

 sufficient for normal maintenance and growth. Latest developments 

 also indicate that an animal will utilize a diet containing animal 

 proteins, better than one made up of plant proteins. This conception 

 is based preeminently upon the supposition that animal proteins 

 have a composition more nearly related to body protein than do plant 



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