CAROTINOIDS IN THE VERTEBRATES 137 



epidermal xanthosis in diabetics than in well persons, and the fact 

 that a yellow color, presumably of the same origin, is frequently seen 

 in the palms of the hands and on the soles of the feet of persons with 

 acute sickness/ 1 may have a secondary origin. The normal cause of 

 the disappearance of carotinoids from both plants and animals is an 

 oxidation. This is undoubtedly their ultimate fate in animals unless 

 they are secreted in the milk fat or egg yolk (in fowls) or stored up 

 as adipose tissue and thus protected from oxidation. Where the oxida- 

 tive tone of the body is low, as in diabetes, coupled in many cases 

 with abnormally large intake of carotinoids, it is not surprising that 

 the pigments should appear in the tissues in abnormally large amounts. 

 This is especially likely to be true of the epidermal tissues inasmuch 

 as the effect of eating carotinoid-rich diets in normal persons shows 

 that the subcutaneous glands can serve as an excretory medium for 

 these pigments. 



Carotinoids in Birds 



The chromolipoid pigments of birds offer many of the most inter- 

 esting problems in the field of animal chromatology. This is true in 

 spite of the fact that a cursory knowledge of the present status of the 

 question of carotinoid pigmentation in the case of the domestic fowl 

 would lead one to believe that the character of the carotinoid pig- 

 ments found in the feathered animals, as well as the origin of the 

 pigments, has been settled for all species of birds. This belief is not 

 justified. Who knows, for example, whether or not numerous species 

 lack carotinoids entirely, as is the case, or nearly so, with many 

 domestic mammals? This is a relatively simple problem to solve. 

 But what shall one say of the problem of determining why the type 

 of carotinoid in the hen is different from that of the cow; or of the 

 problem of ascertaining why the xanthophyll of the yolk of the hen's 

 egg appears to be chemically an isomer of plant xanthophyll in spite 

 of the fact that the plant xanthophyll is the source from which the 

 hen derives the pigment for the egg yolk; or of the problem of explain- 

 ing the w r ide variation in the appearance of carotinoid in the epidermis 

 of fowls, in all of which the adipose tissue is highly colored with 

 xanthophyll, as well as the egg yolk? What might be expected to be 

 simply physiological problems in connection with the behavior of 

 carotinoids in the animal organism turn out to be complicated, or at 



1 Van den Bergh, Muller and Broekmoyt-r (1920) state tbat this phenomenon has been 

 described for a long time by French physicians under the name "signe palmaire." 



