ANIMAL CHLOROPHYLL 381 



a derivative of haemoglobin. In the first place the same 

 elements are present in melanin and in haemoglobin (Ham- 

 marsten and Hedin, 1915, p. 84). Aside from nitrogen and 

 sulphur the most noticeable element present is iron. The 

 earlier observers (Scherer, 1841 ; Berdez und Nencki, 1886) 

 failed, to detect iron, but, as Halliburton (1898, vol. i, p. 121) 

 points out, their failure was due to the fact that they extracted 

 the pigment with hydrochloric acid and thus removed the 

 iron. Morner (1887), and Brandl und Pfeiffer (1890) found that 

 melanin contained a large amount of iron, and believe as 

 a result that melanin is a derivative of the blood-pigments, 

 Schmiedeberg (1897) obtained similar results for the sarco- 

 melanin from a sarcomatous liver, finding that it contained 

 2'7 per cent. iron. The more recent work on the subject 

 likewise corroborates the observation that iron is present in 

 melanin (Gortner, 1912 a; von Fiirth und Jerusalem, 1907; 

 Piettre, 1911 a). 



There is, therefore, both biological and chemical evidence in 

 favour of the view that melanin is derived from the blood- 

 pigments. Moreover, as the present paper has attempted to 

 show, the great majority of invertebrate pigments are not 

 only derived from the pigments of blood-systems but the 

 invertebrate blood-pigments are themselves derived from 

 food. Unless a profound change has occurred in the physio- 

 logical processes of the vertebrates as compared with those of 

 the invertebrates — which is not probable — it appears reason- 

 able to the writer to admit that some at least of the vertebrate 

 pigments likewise owe their origin to the pigments of the blood. 



Urochrome. — The recent feeding experiments of Eoaf 

 (1921) have given strong evidence that the output of urochrome 

 from the urine of guinea-pigs and of man is roughly propor- 

 tional to the amount of chlorophyll taken in as food, and Eoaf 

 suggests, in view of the chemical similarity between the two 

 pigments (the pyrrol reaction), that urochrome is derived from 

 chlorophyll. It is evident that this observation throws quite 

 a new light upon the debated question of urinary pigments, 

 and it gives an added instance of the dependence of animals 



