THE IMPORTANCE OF "IMPURITIES" AND TRACE SUBSTANCES 69 



and functioning of plants and animals, including most micro- 

 organisms. Vitamins are as a rule found in foods, while hormones 

 — often called "endocrines" — are produced by the organism, com- 

 monly by "glands of internal secretion" whose potent products 

 enter the blood. For many years the criteria of food value were 

 fat, carbohydrate, and protein. Calcium and iron, and later 

 iodine, were regarded as essential minerals. Then it was found 

 that protein foods must contain a certain number of essential 

 amino acids. Since most proteins are deficient in some of these, 

 a variety of proteins in the diet is necessary. Though gelatin is 

 a valuable and readily assimilated protein food, it lacks trypto- 

 phane. 9 



In Java, C. Eijkman (Nobel prize, 1929) carried out the pioneer 

 work (1890-97) on polished rice as the cause of beriberi. Professors 

 E. H. Starling and William M. Bayliss of the University of London 

 coined the word "hormone" in 1902; but not until 1911 did Dr. 

 Casimir Funk suggest the word "vitamine" for the vital amine 

 found in unpolished rice. The term vitamin quickly came to 

 stand for unknown essential trace substances in foods. The isola- 

 tion, identification, synthesis and biological understanding of 

 vitamins and hormones are brilliant examples of scientific prog- 

 ress, and have led to great advances in nutrition and medicine. 10 



Dr. Wm. J. Robbins, Director, New York Botanical Garden, has 

 kindly prepared the following resume of some of his work. 



It is now generally recognized that plants require vitamins and 

 similar growth substances. Most plants synthesize the vitamins they 

 need from simpler and more elementary substances. Only the minority 

 — and these chiefly the lower plants — suffer from vitamin deficiencies; 

 that is, they cannot develop unless the material upon which or in 

 which they grow contains some of the vitamins they require, but are 

 unable to make. Some bacteria, yeasts and filamentous fungi must be 

 supplied with vitamins; others are autotrophic for these substances. 

 All the higher plants, with the possible exception of the saprophytic 

 or parasitic forms, are autotrophic for vitamins, though the isolated 

 roots of some of them have been found to require an extra cellular 

 supply of thiamine, nicotinic acid or pyridoxine for growth. 



Schopfer demonstrated in 1934 that Phycomyces blakesleeanus did 

 not grow without the presence of thiamine in the culture medium. 

 Robbins and others found that many fungi have one or more vitamin 

 deficiencies. The deficiency may be complete (the fungus does not 

 grow in the absence of the vitamin from the medium) or partial (the 

 fungus grows slowly in the absence of the vitamin, but more rapidly 



