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Dr. C. A. MacMunn. 



ment, and so on. Hence the conclusion follows that the integu- 

 mental colouring-matter is prepared by the liver, or organ answering 

 to the liver. The next question which suggests itself is this : from 

 what constituent in the liver are the pigments built up ? I am 

 inclined to think that tetronerythrin is probably built up from a 

 lutein pigment, as they are respectively soluble in the same media, 

 and concentrated solutions of both, of sufficient depths, have the same 

 peculiar absorptive powers for the violet end of the spectrum. 

 Tetronerythrin occurs in abundance, both in the coloured hypoderm 

 and exoskeleton of Homarus and Cancer pagurus, and lutein is 

 present abundantly in their livers ; in Carcinus mcenas lutein is present 

 in both situations. Preyer* called attention long ago to the fact that 

 the larva of Ohironomus contains haemoglobin, and yet lives on purely 

 vegetable substances ; so also does a sheep, a cow, or any other purely 

 herbivorous Vertebrate, and yet haemoglobin is manufactured in large 

 quantity in their bodies. f It is likely that the radicals which furnish 

 the colouring-matters in the plant would be made use of by the animal, 

 in the synthetical production of such bodies as haematin or haemo- 

 globin for instance, and just as there is a close relationship between 

 lutein and tetronerythrin, so there is certainly a close relationship 

 between lutein and haemoglobin. For instance, in an egg the only 

 pigment present is lutein, and therefore, if one colouring-matter is 

 derived from another, the haemoglobin of the chick must be in the 

 first instance derived from the lutein of the yolk. Again haemo- 

 globin when extravasated into the ovary, gives rise to a pigment 

 presenting a close relationship with that of egg-yolk, so much so that 

 it has been called lutein. For the present I may call attention to the 

 fact that in some cases the simultaneous presence of haemochromogen 

 and chlorophyll has been demonstrated in the livers of Pulmonate 

 Mollusca, and the amount of one seems to depend on that of the 

 other, for instance, when there was much haematin present there was 

 little chlorophyll, and vice versa; this would seem to show that the 

 possibility of the construction of haematin from chlorophyll suggests 

 itself, and must not be forgotten. 



Bilirubin is an undoubted haemoglobin derivative (as I shall show 

 further on), and according to Gautier^ its formula approaches that of 

 chlorophyll very closely ; the body chlorophyllan obtained in crystals 

 from an alcoholic solution of chlorophyll gave numbers which led 

 Gautier to the formula CjgH^NgC^, which is not far removed from that 

 of bilirubin, C 16 H 18 N 2 3 . 



* " Die BlutkrystaJle," 1871. 



f And haematin in the bile of some of them, as shown in a former paper. " Proc. 

 Roy. Soc," 1880, vol. 31, p. 206. 



% " Comptes Eendus," 1879. " Bot. Zeitg.," 1880. See also Hoppe-Seyler, 

 " Berich. Deut. Chem. Ges.," 1879, and " Bot. Zeitg.," 1879. 



