74 THE VITAMINES 



(193), dealing with the harmful effect of an exclusive protein diet on 

 rats, can very likely be attributed to the insufficient amount of 

 vitamines supplied, although it might also have been due to a relative 

 lack of salts. In a special case, Maignon (194) noted that when he 

 fed rats on egg albumin, together with some salts, they developed 

 a disease which he held to be an acute intoxication of the central 

 nervous system, from which the rats died in a few days. It is not 

 improbable that it was some sort of an avitaminosis. 



Regarding dietary factors such as nucleins, lipoids, etc., it is quite 

 apparent that they are synthesized in the animal body. It is often 

 specified that for certain animals, and also for man, the animal 

 proteins are preferable to the vegetable proteins. In practice this 

 is quite true, and it may be explained in many different ways. In 

 the first place, when we speak ordinarily of animal and vegetable 

 protein, we have in mind the natural products containing those 

 proteins. Now, there are great fundamental differences between the 

 two types of foods. When we feed an animal protein, like meat, 

 eggs, etc., we give the protein, which is very poor in other dietary 

 components, like fat, and especially carbohydrates, in very concen- 

 trated form. With plant products it is different; they contain 

 protein in a very much smaller concentration, accompanied, for the 

 most part, by large amounts of carbohydrates. That this may be of 

 importance, we shall see later. Furthermore, it is possible that the 

 amino acids of animal proteins, because of their close resemblance 

 in composition to those of the body proteins, are better utilized; 

 besides this, they may contain known and perhaps even unknown 

 vitamines carried along during the process of preparation. For 

 example, Osborne, Wakeman and Ferry (I.e. 102) found that it is 

 very difficult to free edestin from vitamine B. As to the relative 

 value of plant and animal protein, we shall go into it more fully in 

 discussing human nutrition. 



When we elaborated the vitamine theory in 1912, we stated that 

 these new substances are important or even indispensable to all 

 plants and animals, predicated upon the then available data. The 

 number of facts which we can bring to our support in proof of the 

 above statement has been greatly augmented since the first edition 

 of this book appeared, although not all types of animals have been 

 investigated in this respect. It is quite true that some animals 

 placed upon a vitamine-free or vitamine-poor diet do not remain 



