90 THE VITAMINES 



served not only as roughage, preventing constipation, but also to 

 dilute the diet and make it more easily utilized. In most cases, the 

 diet consisted of 25 per cent casein, 38 per cent dextrin, 15 per cent 

 butter, 5 per cent salt mixture, 2 per cent agar and 15 per cent dried 

 yeast. With less casein, butter, yeast and salts, and more dextrin, 

 in making up a diet which is very good for rats, no growth was 

 observed in chickens. The experiments lasted from three to four 

 months and it still remains to be seen whether with this regime the 

 experiments can be duplicated, for only then can we regard the 

 problem of the synthetic nutrition of chickens as solved. Filter paper 

 seemed to be the best substance to use for roughage, although an 

 addition of 10 per cent animal charcoal was also effective. 



Palmer (253) carried out a series of experiments in which he tried 

 to raise animals, and particularly chickens, on a diet completely free 

 from plant pigments. The experiments are of special interest because 

 of their relationship with the antirachitic vitamine, to be referred 

 to later. Palmer found that some of the animal pigments belonging 

 to the carrotinoid group, have their origin in the vegetable kingdom. 

 The species having a colored adipose tissue obtain this pigment from 

 the blood, in which it is easy to demonstrate its presence. In a series 

 of feeding experiments with chickens, Palmer and Kempster (254) 

 showed that in some foodstuffs a certain relationship exists between 

 the carrotinoid and the vitamine A content; they demonstrated, 

 however, that this relationship is only apparent and that the pig- 

 ments, per se, play no part in metabolism. They also experienced 

 considerable difficulty in raising the chickens in a closed room, and 

 further, in rinding a diet free from pigments. In the end, they chose 

 a diet composed of white corn, bran from the white corn, bleached 

 flour, centrifuged milk, and bone meal. The chickens used were 

 white Leghorns and weighed from 700 to 750 grams at the start; 

 the colored parts of the body, like the beak, and the feather quills, 

 were only weakly colored; the mortality was quite high. After six 

 months, there were only five out of eleven chickens still alive which 

 had doubled their weight and begun to lay eggs. The eggs were not 

 completely pigment-free, but were nevertheless only weakly colored. 

 Very young chickens could not be raised on this diet. Better results 

 were obtained when filter-paper was added, according to the method 

 of Osborne and Mendel. 



