138 CAROTINOIDS AND RELATED PIGMENTS 



least baffling. For example, it would not seem unlikely that xantho- 

 phyll, readily soluble in fat, would act like a fat dye in the body of 

 the hen. However, when Palmer and Kempster (1919b, c) fed Sudan 

 III to a carotinoid-free cockerel, the dye quickly appeared in the 

 adipose tissue and bone marrow, but not in the visible skin parts 

 (shanks, beak, ear lobes, etc.), whereas xanthophyll, when fed to a 

 carotinoid-free cockerel of the same breed appeared in the shank skin 

 within 72 hours, and annatto, a different fat dye, did not appear in tin- 

 body at all. Again, when Sudan III was fed to a laying carotinoid- 

 free hen, the dye quickly appeared in the egg yolks and deeply stained 

 the adipose tissue, whereas xanthophyll, when fed to a carotinoid-free 

 laying hen appeared only in the egg yolk, the adipose tissue and epi- 

 dermis being unaffected even after a month of xanthophyll feeding. 

 How are these interesting observations to be explained? 



Egg yolk. It is to be expected that the pigment of the yolk of 

 hen's eggs should be the first of the bird chromolipoids to attract the 

 attention of the physiologists. Stadeler (1867) was the first to attempt 

 to secure crystals of the pigment. He failed to do so, but observed 

 the solubility of the pigment in ether and chloroform with a golden 

 yellow color, in CS 2 with an orange color, its unsaponifiability, and 

 the fact that HN0 3 , containing N0 2 , imparted a dirty blue-green 

 color to the impure pigment, while a trace of con. H 2 S0 4 had the same 

 effect. Thudichum (1869), as already mentioned, included the pig- 

 ment among his luteins. Capranica (1877) mentioned having noticed 

 the similarity in properties of the pigment with that of the corpus 

 luteum. The first detailed description of the spectroscopic absorption 

 properties of the egg yolk pigment was given by Kiihne (1878). 

 Careful drawings of the pigment spectrum in ether, petroleum ether 

 and CS 2 in comparison with a similar spectrum of the corpus luteum 

 pigment, show differences now readily explained in the light of our 

 knowledge regarding the t}*pe of carotinoid involved in each case. 

 Kiihne, as already mentioned, decided against an identify of the two 

 pigments on spectroscopic grounds and also because the egg yolk pig- 

 ment failed to give the blue color reaction with iodine previously noted 

 for the corpus luteum pigment. Of interest is Kiihne's observation 

 that the egg yolk pigment is soluble in bile. Palmer and Eckles 

 (1914d) have attached some significance to the fact that plant xantho- 

 phyll is soluble in bile (ox) while carotin is not, as a possible explana- 

 tion of some of the physiological differences between these types of 

 carotinoids in the animal body. 



