578 voegtlin: role of vitamines in nutrition 



beans, brewers' yeast, and many other raw products. These 

 same extracts were also shown to have some curative value in 

 cases of human beri-beri. 



Before entering into the question of the chemical isolation of 

 these curative substances, I should like to call attention to the 

 work of some American investigators which furnished additional 

 evidence as to the importance of some accessory food constitu- 

 ents essential for normal growth. McCollum, Osborne, and 

 Mendel found that a diet of purified protein, fat, carbohydrates, 

 and mineral salts was inadequate for the maintenance of the 

 normal growth of young rats. These discoveries were in contra- 

 diction to the previously held conceptions of growth. The diet 

 of these rats was in every respect balanced from the point of 

 view of its content of protein, carbohydrate, fats, and salts, yet 

 normal growth was not observed in rats fed exclusively on this 

 artificial diet. There was obviously something lacking in this 

 diet, which was essential for normal growth. 



CHEMICAL ISOLATION OF VITAMINES 



Having definitely established the presence in certain foods of 

 unknown accessory food components, it became a matter of con- 

 siderable importance to determine their chemical nature and 

 physiological action. An enormous amount of energy and time 

 on the part of investigators interested in this question was 

 necessary to obtain our present knowledge of these substances. 

 Preliminary experiments showed that the antiscorbutic and anti- 

 neuritic substances 2 could be extracted from certain foods by 

 means of water. The antineuritic substances were also found 

 to be soluble in alcohol. By submitting these primary extracts 

 to further chemical purification various workers succeeded in 

 preparing fractions which seemed to be fairly pure and possessed 

 high curative properties. We are especially indebted for this 

 pioneer work to Funk and Suzuki and their collaborators. Funk, 

 in 1912, succeeded in devising a method which led to a product 



2 Antineuritic substances prevent beri-beri and polyneuritis in birds. 



