242 ANNUAL, REPORT SMITHSONIAN INSTITUTION, 1920. 



of the vitamins. They bear but a small proportion to the total food 

 supply. When they are withheld from the food, as when chemically 

 pure proteins, fats, carbohydrates, salts, and water are adminis- 

 tered, health deteriorates, and in young animals growth ceases, and 

 if the diet is continued death is the inevitable result. Health can be 

 at once reestablished if the diet is amplified by adding to it a natural 

 food, such as a small amount of milk, for foods as they occur in 

 nature contain the accessory factors necessary for growth and mainte- 

 nance. This consideration is of practical importance to the public 

 generally ; so many are the treated, " purified," and sophisticated 

 foods at present on the market that it is most important to the 

 dietitian to remember that these are but poor substitutes for the foods 

 which are made in nature's laboratory. 



Although biochemists have not yet got so far as to be able to state 

 what is the chemical structure of these vitamins, research has at any 

 rate progressed far enough to make it certain that they are numerous, 

 and it is around three that research has mainly centered. They are 

 products of the plant world, and it is on plants that all animals ulti- 

 mately live. Animals have greater synthetic powers than were for- 

 merly believed to be the case, but so far as is at present known they 

 are not able to synthesize or manufacture vitamins. 



The vitamins can be separated by their varying solubilities in 

 water and other agents, and can be distinguished by their varying 

 powers of resistance to heat and other drastic agencies, and further 

 they are differently distributed in various parts of the vegetable 

 world. Their absence prevents healthy growth and leads to death, 

 but the symptoms manifested are different in the three cases. The 

 diseases due to their absence are very conveniently grouped together 

 as " deficiency diseases." Among such diseases are beriberi, and 

 coming nearer home, scurvy and rickets. 



The first of these vitamins is contained in the embryo or germ of 

 cereal seeds. When milling is carried to a high degree this portion of 

 the grain is removed — hence, polished rice, and superfine white wheat 

 flour, though they may appeal to the aesthetic sense, are of inferior 

 value as foods. It is now firmly established that beriberi, the disease 

 of the rice-eating nations, is due to the use of polished rice, and can be 

 prevented or cured by adding the polishings to the diet. Polished 

 rice produces the disease not because it contains a poison, but because 

 it lacks the vitamin. Using the noncommittal nomenclature intro- 

 duced by American physiologists, it is now usual to speak of this 

 vitamin, on account of its solubility in water, as " Water Soluble B." 



The second is contained in the majority of animal fats (commercial 

 lard is an exception) , and is particularly abundant in milk fats and in 

 certain fish oils, such as cod-liver oil. It is specially important as a 



