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THE QUARTERLY REVIEW OF BIOLOGY 



feeding the hay itself to rats. Observa- 

 tions have shown that shoots of Trades- 

 cantia kept in water culture solution in the 

 dark for some eight weeks had lost only- 

 very little of their vitamine activity. 

 Sunflower seedlings exposed to the light 

 and then kept in the dark for eight days 

 had apparently lost none of their activity. 

 Because of the above results Coward 

 decided to investigate the persistence of 

 vitamine A in plant tissues more fully. 

 Her observations show that vitamine A is 

 not used up in any process carried on by 

 living plant tissue in the dark. The 

 vitamine appears to increase when a leaf 

 loses its green color and becomes yellow. 

 Growth obtained with fresh yellow leaves 

 was at least as good as that obtained with 

 the green and appeared to be even better. 

 Withered leaves which had passed through 

 the clear yellow stage, fallen from the 

 tree and died, gave no growth. It appears 

 that vitamine A is not used up in the 

 yellowing autumn leaf until it actually 

 dies. This vitamine was shown also not 

 to diffuse appreciably into water from the 

 cut ends of shoots. 



The presence of vitamines B and C in 

 certain parts of plants has already been 

 shown; no account, therefore, will be 

 given of them here. 



According to Mockeridge, it appears 

 probable that all the animal vitamines are 

 direct products of plant synthesis. It has 

 been ascertained by numerous workers 

 that animals obtain their necessary vita- 

 mines from their plant food. It is now 

 established that plants in their turn require 

 growth-promoting substances which in 

 the case of some of the lower plants are 

 apparently manufactured by themselves, 

 but which in the case of green plants must 

 be supplied from without. Since these 

 necessary accessory substances are essen- 

 tially organic in nature, their only possible 

 source in the case of ordinary green plants 



is to be found in the organic matter of the 

 soil in which they are growing. 



Drummond, Coward, and Watson con- 

 firm the statement of Mockeridge relative 

 to the relation of vitamines in plants and 

 animals. They say that milk secreted by 

 the lactating female will tend to be 

 deficient in vitamines unless her diet 

 contains adequate amounts of these factors. 

 Evidence in support of this view is grow- 

 ing stronger as data accumulate. The 

 value of butter as a source of vitamine A 

 appears to be more dependent upon the diet 

 of the animals than on the length of time 

 that the butter has been in storage. 

 Butter stored at a low temperature 

 does not suffer any appreciable loss of 

 vitamine A. 



According to Funk, it may truly be said 

 that no single division of physiological 

 chemistry has lately been productive of 

 more publications than that of the vita- 

 mines. The reason is, that new facts and 

 observations are obtained with an ease 

 that is truly astonishing. Because of this, 

 many investigators have failed to pene- 

 trate more deeply into this subject. They 

 have satisfied themselves, as a rule, with 

 results obtained by indirect conclusions. 

 This condition of marking time and 

 useless quibbling provides an excellent 

 opportunity for the representatives of 

 destructive criticism, which, here more 

 than in any other field of research, is 

 effective in hindering the solution of the 

 problem. In spite of these difficulties the 

 knowledge of the nature of the vitamines 

 progresses gradually, and we may hope 

 that their chemical isolation is not far 

 distant. 



Until lately the idea was prevalent that 

 for the complete nutrition of an animal 

 organism only proteins, fats, carbohy- 

 drates, salts and water were necessary. 

 However, in the older literature there is no 

 lack of statements which of themselves 



