1903.] Group of Yellow Colouring Matters. 175 



without assuming a green tinge, the bands, however, shift slightly 

 towards the red and gradually fade without the formation of any 

 .additional ones ; the addition of ammonia causes the bands to shift a 

 little towards the violet. It thus appears that bixin is an allied 

 substance to chrysophyll and the other xanthophylls, and as it is 

 ^table and more easy to prepare than the other crystallisable members 

 of the group, it may with advantage form a starting point to study 

 the chemical constitution and relationship of the xanthophylls. 



Yellow Pigment of the Egg Yolk and Fowl Serum. 



The above yellow pigment together with that of the serum of other 

 animals, of fats, butter, of the corpus luteum of the ovary has been 

 the subject of investigation by Thudichum, Hammarsten, Malay, 

 Krukenberg, MacMunn, Halliburton and others. Thudichum was the 

 first to examine the pigment of the corpus luteum and the name Lutein was 

 given to it, which name was extended to the whole group. Krukenberg's 

 word, Lipochrome has, however, generally been adopted by physio- 

 logists. As they are characterised by giving bands towards the violet 

 region of the spectrum, and also by the same colour reactions with 

 H L )S0 4 and HN0 3 in the dry state as exhibited by the xanthophylls, a 

 comparison was made between the yellow pigment of the egg-yolk and 

 serum of the fowl and the xanthophyll of flowers. The pigment 

 of the egg-yolk can be extracted by treating the yolk freed from the 

 white with alcohol in excess, which precipitates the proteids which 

 take up the pigment leaving the filtrate colourless. If the precipitate 

 be now treated with hot absolute alcohol, the yellow pigment is 

 dissolved and the separation by carbon-bisulphide applied. In the 

 case of the serum the blood-clot is allowed to stand twenty-four hours, 

 broken up and the serum filtered off ; it is of a deep yellow colour but 

 more or less masked by the red corpuscles held in suspension. Alcohol 

 is now added in excess, and the yellow pigment which is carried down 

 by the precipitated proteids is extracted with hot absolute alcohol and 

 the separation by carbon-bisulphide is performed. They both form 

 bright yellow alcoholic solutions and the spectrum of each is identical 

 with that of L. xanthophyll, and from the examination of the crude 

 extracts and the carbon-bisulphide fractions the pigment appears to 

 consist of this colouring matter only, with an almost total absence of 

 those colouring matters that obscure the violet and ultra-violet 

 (Plate 7, figs. 5 7). The action of acids upon the spectra is identical 

 with the action upon L. xanthophyll (Plate 7, figs. 813), and the 

 colour reactions in the dry state with HC1, HoS0 4 and HN0 3 are 

 .also the same, the blue coloration being not quite so brilliant, which 

 may be accounted for perhaps by the presence of fats. In the case of 

 the egg-yolk an attempt was made to get rid of the fats by saponifica- 



