278 LIFE : OUTLINES OF GENERAL BIOLOGY 



of the grains began to be striking when the rice-eating districts of 

 the East were invaded by milling machinery from the West. 



When our sailor forefathers went a long voyage with salt beef 

 and the like as the main part of their sustenance, they did not get 

 on well without vitamins, for they became afflicted with the horrible 

 disease of scurvy, which is due to the absence of one of these power- 

 ful "accessory food-factors". We have changed all that, and scurvy 

 has gone by the board. Apart from the shortening of voyages from 

 port to port and the increased possibilities of carrying varied food 

 for the voyage, the "deficiency disease" of scurvy can be kept 

 away by serving out lime-juice. Some such precaution is now com- 

 pulsory. In old days no one understood scurvy, but it is interesting 

 that sailors should have chewed the common "scurvy-grass", or 

 it might be dulse and other seaweeds, when they reached a shore. 

 It was as if they felt that they needed something of that sort, and 

 it is possible that some of the queer vagaries of appetite among 

 animals and among children may be unconscious gropings after 

 needed vitamins, which are formed primarily and mainly in the 

 tissues of green plants. 



The precise r61e of the indispensable accessory foodstuffs is still 

 uncertain, but we may think of two possibilities, (a) It is possible 

 that vitamins are essential constituents of the living matter of 

 protoplasm, just as proteins are, and that they cannot be built 

 up in the animal body, but have to be borrowed, as it were, from 

 plants, or from the milk of vegetarian animals, and so on. The 

 sickly child becomes vigorous when it gets supplies of cod-liver oil. 

 The cod ate the whelk, which ate the worm, which throve on the 

 minute green organisms of the sea. In other words, vitamins may 

 pass from one embodiment or incarnation to another, although the 

 animals concerned in the chain may not be able to manufacture 

 them for themselves. 



{b) But another view is that vitamins owe their value to some 

 tonic influence which they exert on the chemical routine (or 

 metabolism) of the body. They may be stimulating rather than 

 nutritive. They are not ferments, but their virtue may be in acting 

 as "catalysts". This means, as is explained in another study, that 

 they accelerate chemical reactions which would otherwise be too 

 sluggish to be of much avail. 



Vitamins were practically discovered about twenty years ago 

 by Prof. Sir Frederick Gowland Hopkins, the distinguished bio- 

 chemist of Cambridge, but many experts have shared in their 

 investigation. Let us notice briefly the various kinds that have 

 been distinguished. (A) The fat-soluble vitamin A, first detected 

 in butter and yolk of egg, is abundant in cod-liver oil and in many 

 vegetable oils. Its primary source is in green leaves and seaweeds. 

 It seems to promote growth and to have something to do with the 



