HORMONES, AUXIMONES, VIT AMINES, AND TOXINS 243 



ficial effects; while such specific names as " fat-soluble A," 

 " water-soluble B," etc., have been used to designate individual 

 types of these accessory food substances. However, the term 

 vitamine is such a convenient one and is so generally recognized 

 and accepted that it will probably continue to be used, at least 

 until some more definite knowledge of the nature and composition 

 of these growth-promoting, disease-preventing, and reproduction- 

 stimulating food constituents is obtained. 



The following definition of the term " vitamines " gives a 

 satisfactory conception of the nature and functions of these 

 substances, so far as they are yet known. " Vitamines con- 

 stitute a class of substances the individuals of which are necessary 

 to the normal metabolism of certain living organisms, but which 

 do not contribute to the mineral, nitrogen, or energy factors of the 

 nutrition of those organisms." As sub-groups of the vitamines, 

 there have already been recognized the growth-promoting, fat- 

 soluble A; the antineuritic B, and the antiscorbutic C. 



Until very recently, the investigations of vitamines have dealt 

 exclusively with their relation to human nutrition; although 

 it has been generally believed that the vitamines themselves are 

 elaborated only by plants. It was generally recognized, however, 

 that those plants, or parts of plants, which are capable of very 

 rapid growth or metabolic changes, such as germs, spores, leaves, 

 etc., are generally the richest source for vitamines for animal needs. 

 Hence, there seemed to be considerable basis for the assumption 

 that the elaboration of these substances by plants is definitely 

 connected with their own metabolic needs. Recently, inves- 

 tigations of the functions of vitamines in the growth of plants 

 have been begun. These are still in progress, but the following 

 conclusions seem to be justified at the present time: (a) Potato 

 tubers appear to contain growth-promoting substances which 

 are essential to the proper growth of the sprouts. Whether these 

 are the same substances which are efficient in the prevention of 

 scurvy in men has not yet been investigated. (6) Baker's yeast is 

 probably dependent upon a supply of vitamines in the medium 

 in which it is to grow. Yeast itself, after having grown in barley 

 wort, is one of the most important sources of vitamines for animal 

 uses or for purposes of investigations of vitamine activity. But 

 it has been reported that a yeast cell will not grow in an artificial 

 medium which contains all the essential nutrients for yeast but 



