1316 LUTEINS. 



a third faint band near Gr may be seen, especially if the resi- 

 due from the ethereal extract be dissolved in carbon-bisulphide 

 and examined. If the residues from the ethereal extracts of 

 egg-yolk and corpora lutea be saponified and extracted with 

 carbon-bisulphide, the solutions yield identical absorption 

 spectra. 



2. Serum lutein. 



The serum from the blood of almost all animals is usually 

 of a more or less yellow colour; it is specially marked in the 

 case of the horse and ox, is also marked in the case of sheep 

 and man, and is but slightly present under normal conditions 

 in the serum of the dog, rabbit or cat. The colour has by 

 different observers been ascribed to different pigments. In 

 some cases it may be due, at least partly, to the presence of 

 bile-pigments or their derivatives, these being much increased 

 in certain diseases such as jaundice. But in addition to these 

 it appears that the colour of all pigmented serums is due to a 

 specific pigment, which while it may differ (?) slightly as 

 obtained from the blood of different animals, belongs in each 

 case to the general class of substances known as lipochromes. 

 By shaking serum with ethyl or amyl alcohol a coloured extract 

 is obtained which contains a fatty pigment, evidently belonging 

 to the class of lipochromes as judged by the fact that it is 

 soluble in alcohol, ether, chloroform, benzene, carbon-bisulphide, 

 etc., shews the two (in the case of birds only one) bands in 

 the blue part of the spectrum, and gives the chemical reactions 

 (p. 1315) with nitric acid and sulphuric acid characteristic of 

 these substances. It is in many cases identical with the pig- 

 ment which can be extracted from the fat of the animal from 

 whose blood the serum was obtained. Serum lutein is bleached 

 by the action of light. 



3. Tetronerythrin. 



This name was first given to a substance extracted by chloro- 

 form from the red excrescences over the eyes of certain birds. 

 It was described later as occurring in some sponges, fishes and 

 feathers. More recently it has been found as a pigmentary 

 constituent of the blood of Crustacea. The pigment is readily 

 soluble in alcohol, ether, chloroform, benzene and carbon- 

 bisulphide, is readily bleached by light, yields the chemical 

 reactions with sulphuric acid and nitric acids which are char- 

 acteristic of the lipochromes (see p. 1315), like these shews 

 an absorption band near F somewhat similar to that of xan- 

 thophane and rhodophane, and is slowly bleached by the action 

 of light. 



