VITAMIN C 159 



guinea pig is of interest as offering a possible explanation of the varying 

 requirements of different species of animals. 



Of great importance in this connection was the demonstration by 

 Parsons (1920) of the persistence of the antiscorbutic substance in 

 the liver of the rat after long intervals on a scorbutic diet. In an effort 

 to explain the apparently marked differences in antiscorbutic require- 

 ment of the tvi^o rodents, the guinea pig and the rat, a comparison 

 was made of the antiscorbutic content of the rat's body tissues (1) 

 when a typical scurvy diet was fed and (2) when the diet was 

 high in antiscorbutic substances. The liver and muscle tissues of 

 both groups were fed to scorbutic guinea pigs and for purposes of 

 comparison fresh fish tissue was also used. The muscle tissues could 

 not be fed at a high enough level to effect a cure but the liver tissues 

 of both groups of rats showed a high content of antiscorbutic sub- 

 stance, practically no differences in the growth curves or alleviation 

 of scorbutic symptoms of the guinea pigs on the two diets being 

 noticeable. 



These results were thought to indicate the need for the antiscorbutic 

 vitamin by the rat, thus confirming in part the conclusions of Harden 

 and Zilva and of Drummond, and to suggest the possibility that the 

 rat is capable of synthesizing this substance. Other hypotheses ad- 

 vanced by Parsons at this time were as follows: "The antiscorbutic 

 substance may pass into a modified form in foods on ageing, drying, 

 etc., and this form may not be utilizable by the guinea pig but be utilized 

 by the rat. The rat's requirement for antiscorbutic substances may be 

 strikingly low. The rat's requirement for antiscorbutic substances may 

 approximate that of the guinea pig from the standpoint of metabolism 

 but there may be less waste of the substance due to a different rate 

 of excretion." 



An extension of these observations, using diets more carefully freed 

 from the antiscorbutic substance and continuing the feeding into the 

 second generation, was reported simultaneously by Lepkovsky and 

 Nelson (1924) and Parsons and Hutton (1924), who found that the 

 livers of second generation rats on these highly purified diets showed 

 no diminution in antiscorbutic substance. This was thought to disprove 

 (or weaken) the suggestion that the rat's requirement for the anti- 

 scorbutic factor is very low. In striking contrast with these observations 

 was the discovery by Parsons and Reynolds (1924) that the livers of 

 guinea pigs on a scorbutic ration contain inappreciable amounts of 

 vitamin C although the livers of normal guinea pigs contain it in 

 abundance. This discovery was thought to emphasize the reasonable- 



