348 NUTRITION OF FARM ANIMALS 



definiteness what proportions of the different ash elements are 

 required in maintenance rations and the whole subject offers 

 a wide field for investigation. 



3. ACCESSORY SUBSTANCES 



Leaving out of account the fact that the proteins are a minor 

 source of energy and considering (3nly the requirements for 

 matter, the proteins and ash elements of the feed are required 

 substantially for maintenance, i.e., to make good losses of the 

 structural elements of the body, especially if the ash content 

 of the body fluids be included under this designation. Recent 

 investigations, however, have revealed the presence in the feed 

 of minute amounts of substances which appear to bear quite 

 a different relation to nutrition and which may be called for 

 convenience, accessory substances. 



437. Vitamins. Attention was first called to these acces- 

 sory substances through investigations into the cause of the 

 tropical disease known as beri beri. It has been shown that 

 this is a nutritional disease, resulting from a preponderance in 

 the diet of so-called " polished " rice, i.e., rice from which the 

 seed coats have been removed. It is a tropical disease only in 

 the sense that many inhabitants of the tropics subsist largely 

 on rice. It has been shown that it can be produced in Europe 

 by the excessive use of this grain. 



Substantially the same disease (polyneuritis) may be induced 

 in animals, especially in fowls, by an exclusive diet of polished 

 rice and it is to experiments on these animals that most of our 

 imperfect knowledge of the subject is due. 



It has been shown that in man beri beri may be prevented 

 by the use of a rational dietary, and especially by the substitu- 

 tion of rough rice or of other grains for polished rice. Experi- 

 ments On animals have shown that a subject fed on polished 

 rice until nearly at the point of death may be restored to normal 

 condition in a short time by the administration of small amounts 

 of an aqueous extract of rice bran, the improvement being so 

 rapid as to appear almost miraculous. The generally accepted 

 explanation is that the bran contains a small amount of a water- 

 soluble substance or substances necessary for the normal func- 

 tioning of the body, the lack of which in polished rice gives 



