CHEMICAL BASIS OF THE ANIMAL BODY. 269 



belongs in each case to the general class of substances known as 

 lipochromes. This view was originally put forward by Thudichum \ 

 who ascribed the colour to the pigment lutein which has been already 

 described. This view is probably correct, independently of the possi- 

 bility that the colour may be in some cases due partly to the simul- 

 taneous presence of bile pigments or their derivatives. Thus it is 

 found 2 that 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, benzol, carbon bisulphide &c., shows the two 

 (in the case of birds only one) bands in the blue part of the spectrum, 

 and gives the chemical reactions (p. 265) with nitric acid and sulphuric 

 acid characteristic of these substances. It is in many cases identical 

 with the pigment 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 chloroform 

 from the red excrescences over the eyes of certain birds 3 . It was 

 subsequently investigated by Hoppe-Seyler (from the same source), 

 and described later as occurring in some sponges 4 , fishes 5 and feathers 6 . 

 More recently it has been found as a pigmentary constituent of the 

 blood of Crustacea 7 . The pigment is readily soluble in alcohol, ether, 

 chloroform, benzol and carbon bisulphide, is readily bleached by light, 

 yields the chemical reactions with sulphuric acid, nitric acid and iodine, 

 which are characteristic of the lipochromes (see p. 265), like these 

 shows an absorption band near F somewhat similar to that of xantho- 

 phane and rhodophane (p. 265), and is slowly bleached by the action 

 of light. 



The pigments of the animal body which have been so far dealt 

 with admit of a certain amount of classification with reference either 



1 Centralb. f. d. med. Wiss. 1869, S. 1. 



2 Krukenberg, Sitzb. d. Jena. Gesell. j. Med. u. Naturwiss. 1885. Halliburton, 

 Jl. ofPhysiol. Vol. vn. (1885), p. 324. 



3 Wurm, Zt. f. iviss. Zool. Bd. xxxi. (1871), S. 535. 



4 Krukenberg, Centralb. f. d. med. Wiss. 1879, S. 705. 



5 Krukenberg, Vergleich.-physiol. Stud. 1 Heine, Abth. 4, 1881, S. 30. 



6 Krukenberg, Ibid. Abth. 5, S. 87. 2 Eeihe, Abth. 1, S. 151. See also Merej- 

 kowski, Compt. Rend. T. xcm. (1881), p. 1029. Mac Munn, Proc. Roy. Soc. Vol. 

 xxxv. (1883), pp. 132, 370. 



7 Halliburton, Jl. of PhysioL Vol. vi. (1884), p. 324. 



