SCURVY 65 



than the guinea-pig (four to eight times) and, 

 arguing from the length of time required for the 

 development of the symptoms, that the human 

 being is again much less susceptible than the monkey. 



It is a surprising fact that an animal so closely 

 allied to the guinea-pig as the rat should never- 

 theless be very much less susceptible to scurvy. 

 To such a degree is this the case that it is commonly 

 supposed that the rat can flourish and produce and 

 rear young in an entirely satisfactory manner and 

 without exhibiting any symptoms of scurvy on 

 diets free from the antiscorbutic factor, such as 

 those used by McCollum and his colleagues in their 

 experimental work on the accessory factors. These 

 consist of purified caseinogen, starch, and salts, with 

 the addition of clarified butter fat and autolysed 

 yeast. It has, however, been observed ^ that the 

 addition of orange juice to this diet produces a 

 pronounced improvement both in the general con- 

 dition of the animal and in the rate of growth and 

 the maximum weight attained. 



It may therefore be regarded as proved that the 

 antiscorbutic factor is an essential constituent of 

 the diet of the higher animals, the absence of 

 which is in all cases incompatible with the proper 

 development of the animal and may lead to serious 

 lesions and ultimately to death. 



* Harden and Zilva, Biockem. J., 1918, 21, 408, confirmed by 

 Drummond, Biochem. J., 1919, 13, 77. 



F 



