274 CAROTINOIDS AND RELATED PIGMENTS 



sarily with great frequency, is required to prevent the excretion of 

 xanthophyll by way of the skin, and thus brings about a gradual fading 

 of the visible skin parts. Whether there is a mobilization of pigment 

 in other organs of the body, such as the liver, was not determined in 

 our experiments. 



Rosenheim and Drummond (1920) have expressed the view that this 

 deflection of xanthophyll to the ovaries during egg laying indicates that 

 the pigment is required for a definite and important function in the 

 egg and that this fact thus supports the theory that the carotinoids are 

 related to the vitamins. It is just as reasonable to suppose, however, 

 that the egg yolk is an easier path of excretion for a fat-soluble pig- 

 ment than is the skin, just as the kidneys are ordinarily the chief path 

 of excretion of water-soluble waste products. Nevertheless, it might 

 be worth while to investigate the relation between this whole phenome- 

 non and the more recent interpretation of the effect of Nile blue on 

 the pigment granules in the epidermis of the chicken skin, namely, that 

 the pigment is transported there in association with fatty acids. It is 

 possible that the concentration of the fat synthesizing powers of the 

 hen in the ovaries during egg laying prevents the secretion of fatty 

 acids by the blood capillaries and thus causes a concentration of xan- 

 thophyll in the fat laid down in the ova. This does not explain, how- 

 ever, why Sudan III, a fat dye, never appears in the skin when fed to 

 either laying or non-laying fowls, although it appears abundantly in 

 the egg yolk, bone marrow and adipose tissue, and feathers. 



A phenomenon somewhat analogous to the fading of the skin of fowls 

 during egg laying has been observed in the case of salmon during their 

 fresh-water migration to the spawning beds from the sea, during which 

 time the animals starve. As described by Miss Newbigin (1898), the 

 flesh of the fish has the familiar strong pink color and the small ovaries 

 a yellow-brown color when the fish come from the sea. As the re- 

 productive organs develop the flesh becomes paler and the rapidly grow- 

 ing ovaries acquire a fine orange-red color. The explanation of this 

 phenomenon unquestionably lies in the mobilization of the fat stores 

 of the body in the reproductive organs and the shed ova, rather than 

 in a mobilization of pigment itself. It is to be remembered that the 

 fish are taking no food whatever during their migration, and must 

 therefore draw upon every possible reserve, not only for their own 

 needs but also for the reproduction processes for which the journey is 

 taken. Essentially this view of the phenomenon was adopted by Miss 

 Newbigin. 



