904 NUTRITION AND HEAT REGULATION. 



is deficient in this constituent a diseased condition of the eyes 

 develops known as xerophthahnia, which if not treated leads to 

 a severe conjunctivitis, ulceration of the cornea, and even destruc- 

 tion of the eye. When fats such as butter or cod-liver oil con- 

 taining the fat-soluble A are added to the diet the xerophthalmia 

 clears up. A similar disease has been described in children under 

 conditions in which the diet was obviously lacking in fat-soluble 

 A,* and addition of. this element to the diet has been followed by 

 quick relief. Some observers have been convinced that deficiency 

 of this vitamin in the diet is mainly responsible for the appear- 

 ance of rickets, hence its designation as the antirachitic vitamin. 

 Recent work, f however, would indicate that while diets known to 

 be deficient in fat-soluble A may undoubtedly cause in animals a 

 condition of rickets, it is not permissible as yet to refer the result 

 simply to the lack of this vitamin. The etiological factors con- 

 cerned in the production of rickets are complex. Fat-soluble A 

 is fairly resistant to high temperatures. Boihng if not prolonged 

 does not destroy it unless the solution is alkahne. It is stated by 

 Hopkins that it is somewhat readily oxidized. Bubbling air 

 through a solution during heating destroys the vitamin. 



2. Water-soluble B {Antineuritic Vitamin): — A diet deficient 

 in this vitamin produces beriberi in man, and an analogous con- 

 dition of polyneuritis in the lower animals. Feeding experiments 

 demonstrate also that it is essential to growth. Fortunately, it is 

 wide-spread in nature, occurring in practically all foodstuffs, 

 although in varying amounts. Its principal source is the seeds of 

 plants and the eggs of animals, where we may assume it is stored 

 to supply the needs of the growing animal or plant. In peas and 

 beans the vitamin is distributed throughout the seed, but in the 

 cereals it is found mainly in the germ or embryo and in the aleurone 

 cells under the outside membrane or pericarp. As both of these 

 structures are removed in the process of milling to produce flour, 

 it follows that the best wheat flours, cornmeal, rice, etc., are de- 

 ficient in this vitamin, and if they are used too exclusively in the 

 chet may occasion the development of beriberi. Water-soluble B is 

 the most resistant of the vitamins. It is not destroyed by drying 

 or by cooking at ordinary temperatures if not too prolonged. 



3. Water-soluble C {Antiscorbutic Vitamin). — It has long been 

 known from the records of sea voyages and expeditions that 

 scurvy appears when a diet devoid of fresh meats and vegetables 

 is used. It has long been known also that this condition can be 

 obviated or cured by the use of fresh vegetables or meat, or more 



* Bloch, "The Journal of Hygiene," 1921, 19, 283. 



t McCollum, Simmonds, Parsons, Shipley, and Park, "Journal of Bio- 

 logical Chemistry," 1921, 45, 333. 



