GENERAL METHODS — HISTORY OF PROTEIN FOOD. 903 



normal direction and character of the metabohsm. This unex- 

 pected result may be illustrated best by reference to the condition 

 known as beriberi. Beriberi is a disease that occurs chiefly among 

 oriental nations that make great use of rice as a food. The dis- 

 ease takes a variety of forms, but the characteristic symptoms are 

 paralyses, and atrophy and contractures of the limbs. It has been 

 shown that the condition is caused by limiting the diet exclusively 

 or mainly to polished rice, that is, to rice from which the outer 

 layers of the grains have been removed. If the polishings are 

 restored to the diet the condition disappears, or if other materials, 

 such as meat and barley, are used with the polished rice the disease 

 does not occur. When fowls are fed exclusively on polished rice 

 they develop a condition (polyneuritis) similar to beriberi and 

 soon die. They ma}^ be saved by adding the polishings to the diet 

 or by changing the diet. It is evident from such experiments that 

 there is something in the polishings of the rice grain and in the 

 bran separated from other cereals by the process of milling which 

 is essential to normal nutrition. Efforts to isolate this material 

 in a condition of chemical purity have not been successful, but it 

 has been shown that it is a water-soluble substance and that it 

 is present in most of our natural foodstuffs. Funk gave to this 

 constituent and to the factors that play a similar role in nutrition 

 the name of vitamins; others have designated them simply as 

 accessory food factors or they are described in terms of their 

 soluliilities. The great importance attributed to these bodies in 

 nutrition has developed largely out of feeding experiments with 

 purified foodstuff's such as are described in the preceding para- 

 graph. These experiments have shown clearly that a diet of 

 purified foodstuffs, no matter how ample from the standpoint 

 of potential energy, is not capable of providing adequately for 

 growth or maintenance if the so-called vitamins are absent.* 

 Work of this character has shown that there are three at least of 

 these vitamins. They are designated differently by the various 

 workers, but in view of our incomplete knowledge concerning 

 them the preferable nomenclature at present is perhaps that sug- 

 gested l)y AlcCollum, namely, fat-soluble A, water-soluble B, and 

 water-soluble C. 



1. Fat-soluble A {Antirachitic Vitamin) .—This vitamin is 

 found mainly in the animal fats (with the exception of lard) and 

 in the foliage of plants. Feeding experiments demonstrate that 

 it is essential for growth. Children obtain their supply mainly 

 from full milk, butter, or cream, and adults, from these sources 

 or the leafy vegetables. It has been shown in rats that if the diet 



* In this country the pioneer work in this field has been done by Osborne 

 and Mendel, and McCoUum and his collaborators, Davis, Simmonds et al 



