THE VITAMINES IN THE ANIMAL KINGDOM 91 



However, instead of using butter, which is not carrotin free, pig 

 liver was used as a source of antirachitic vitamine. Sixty chicks 

 were placed on this diet, upon which they grew well for about 6 

 weeks, but then began to lose ground. At this stage of the experi- 

 ment, young pigs' liver was given with the result that an immediate 

 improvement was seen. The animals, which were 3 months old, were 

 of normal size and weight and received during the summer an addition 

 of pigment-free vegetables, such as white onions. Palmer and 

 Kempster concluded that young chickens could live without carrotin- 

 oids, if the diet contained sufficient vifcamines. They believed also 

 that the possibility of discovering the nature of vitamine A by an 

 investigation of the carrotinoids was without foundation in fact. 

 The animals fed on a carrotinoid-free diet laid eggs after 6 months, 

 and yet the chickens in the second generation were few in number 

 and rather puny in appearance. 



Hart, Halpin and McCollum (255) and Hart, Halpin and Steen- 

 bock (256) studied the nutritive requirements of chickens. For their 

 experiments, they used half -grown animals fed on a mixture of corn, 

 corn gluten and calcium carbonate, and also wheat, wheat gluten 

 and calcium carbonate. The birds grew well and were able to lay 

 fertile eggs. These findings stood out in marked contrast to the 

 results obtained with rats and pigs, and showed satisfactorily that the 

 nutritive needs of chickens and some mammals were totally dissimilar. 

 In chickens, an addition of salts, casein and butter were without the 

 slightest influence, while the protein concentrates acted favorably. 

 These results might be attributed either to the influence of pro- 

 tein concentration or to the addition of. unknown factors, which 

 are not present in cereals and casein, and which exert a favor- 

 able influence on egg production. The experiments with younger 

 animals (I.e. 256) resulted somewhat differently. In this case, corn 

 was a sufficient source of B- and A-vitamine, but not so with wheat, 

 upon which the animals lived only three months. It was only when 

 salts, casein and butter were added that the diet appeared to be 

 complete. In a similar manner, Harney (257) was able to show that 

 for the production of eggs, the use of plant foodstuffs, in spite of 

 the high protein content, could not be compared to that of animal 

 food, and besides this, Kaupp (258) held that an addition of skimmed 

 milk could influence the production of eggs favorably. 



