268 CAROTINOIDS AND RELATED PIGMENTS 



ingested and thus prevent their deposition in the tissues. This fact 

 alone seems to argue against the carotinoids performing any general 

 physiological function in animals; a priori, a substance of general value 

 in nutrition would most likely have a general occurrence and would at 

 least always be present in the animal body. The complete absence 

 of carotinoids from the tissues and secretions of certain species of ani- 

 mals and their almost complete absence from others, even on diets rich 

 in carotinoid pigments, furnishes a sufficient basis, at least from a teleo- 

 logical standpoint, for rejecting any theory that the carotinoids exert 

 a physiological function in animal life. 



The writer became interested in this question from an experimental 

 point of view in 1912, when it was found, in connection with the bio- 

 logical origin of the lipochromes of cattle, that the new-born calf of a 

 highly pigmented breed of cattle showed an almost complete absence 

 of carotinoids. This suggested the idea of raising animals to maturity 

 on carotinoid-free diets, particularly those species which normally de- 

 posit the carotinoids in their tissues. Later, after the writer (1915) 

 had shown that the lipochromes of fowls are derived from plant xantho- 

 phyll, plans were laid for carrying out such an experiment on these 

 animals, because of the obvious advantages associated with a smaller, 

 more rapidly growing species. 



The problem was primarily one of selecting a ration entirely devoid 

 of carotinoids, particularly xanthophyll, but otherwise adequate for 

 normal growth. The problem had the added interest that the rapidly 

 growing subject of vitamins had already (1916) indicated a casual re- 

 lationship between the occurrence of fat-soluble vitamin A and caroti- 

 noids in certain foods such as butter and green leaves, and the absence 

 of both substances from lard. The experiments showing the possi- 

 bility of raising fowls on diets lacking the natural pigment of their 

 adipose tissue, which were begun in 1916 and were reported by Palmer 

 and Kempster (1919a) were not designed, however, to show the rela- 

 tion between carotinoids and vitamin A. The writer dismissed the 

 possibility of any such relation as the result of the experiment carried 

 out in the winter of 1916-17 in which young chickens weighing 700 

 to 750 grams were raised to maturity and exhibited normal fecundity 

 on carotinoid-free rations. The successful termination of a later ex- 

 periment in this series, in which a flock of 50 chickens was raised from 

 hatching to maturity on similar diets, showed conclusively for the 

 first time that a species of animal which is normally pigmented with 



