THE VITAMINES IN THE ANIMAL KINGDOM 75 



in good condition, even though no symptoms of any of the known 

 avitaminoses are apparent. Nevertheless, these exceptions cannot 

 militate against the general significance of the vitamines for the life 

 processes for many reasons. For one, so long as the experimental 

 animals are kept upon an artificial diet made up of purified con- 

 stituents, they do not live long if extracts of unpurified products 

 are not given. All experiments seeking to demonstrate the contrary 

 have been carried out by feeding a dietary containing either traces 

 of known or unknown vitamines. Then again, it has also been shown 

 that some species of animals can dispense with one or another of the 

 vitamines. This phenomenon may perhaps be explained by the 

 symbiosis of the host with certain bacteria. In the higher animals, 

 these microorganisms are found in the intestinal tract in large 

 amounts and are perhaps able to build up the vitamines from simple 

 substances and convey them to the animal. At the end of this 

 chapter we shall add a short paragraph dealing with the role of bac- 

 teria in animals, but at this juncture, we shall only remark that no 

 attempt has as yet been made to establish these new viewpoints 

 experimentally. 



All these procedures bring us nearer to the point that interests us 

 mostly, namely, accurate knowledge of the subject of human nutri- 

 tion. At once, we are confronted with questions dealing with 

 economic and agricultural problems. Let us consider the breeding 

 of animals as an example. From everything that has already 

 been mentioned it is apparent that the condition of the soil, which 

 contains quantities of organic and nitrogenous matter, can be 

 brought into relationship with the study of vitamines. The indi- 

 cation for such problems is seen in the publication of W. A. Davis 

 (195) who thought that the poverty of the soil (in Bihar, India) 

 in phosphorus is the cause of an avitaminosis in cows, which is 

 responsible for a smaller yield of milk and is connected with the 

 under-nourishment of children. Similarly, a nervous disease of 

 horses was observed in these villages. In European countries, as 

 well as in the United States, where agriculture and cattle raising are 

 carried out rationally, these conditions are of course to be noted 

 very infrequently. It is different in countries like Australia, Argen- 

 tine and South Africa, where cattle raising is carried out on a large 

 scale without paying sufficient attention to the care of the soil, due 

 no doubt to the lack of laborers. There we often hear of diseases, 



