Vitamins 



14 



The role of foods in the life, growth, and health of animals has been 

 a subject of philosophical speculation at least since the classical period 

 of Greece. Suitable foodstuffs were believed to contain a vital sub- 

 stance without which materials were unsatisfactory as foods. This 

 theory persisted until perhaps 1827, when Prout suggested that mam- 

 mals required principles described in terms now replaced with protein, 

 carbohydrate, and fat. 



For decades it was believed that these three classes of materials were 

 the only essential nutrients. Moreover, it was further considered that 

 all proteins were nutritionally alike and that the various carbohydrates 

 and fats were quite equivalent. Therefore, it was believed that the 

 best diets for animals and men were those highest in the three groups 

 of compounds. As a logical extension of this thinking, much effort 

 was expended in the analysis of foods from this point of view. 



In 1871 the siege of Paris imposed great hardship on the inhabitants, 

 and the supply of milk to the city was blocked. Since the proportions 

 of protein, carbohydrate, and fats in milk were known, an emulsion 

 of corresponding composition was proposed as a substitute in the 

 diets of infants and children. As might be anticipated noAV, the results 

 were tragic. Later that year the chemist Dumas wrote an account of 

 the dietary problems arising from the siege and the imitation milk 

 and stated that ". . . no conscientious chemist can assert that the 

 analysis of milk has made known the products necessary to life which 

 that aliment contains." 



Although Dumas clearly realized the critical importance of unknown 

 factors, little concern was given to the new concept. However, in 1880 



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