CHEMICAL BASIS OF THE ANIMAL liom 



during the washing a considerable amount of the sub-tan' e passes 

 into solution. Inn as tin- merely adherent salt- 

 it becomes !.--> and less soluble in water until at la-t it is almost 

 insoluble When dried it takes tin- form of a dark ivddish-bro\vn 

 amorphous j.owdt-r, which is ivadily >'lublc in alcohol andchl>i" 

 form, and but sparingly soluble in pun- ether. It is also 

 soluble in alkaline solutions, to which it impart- a yellow colour 

 a- <if normal urine: when acidulated the >.. Unions turn red. 1 



The acid solutions of hydrobilirubin show a marked absorption 

 band between // and /-'which becomes fainter if ammonia i- added 

 until the reaction is alkaline. But on the subsequent addition of 

 a few drops of a solution of zinc chloride, the band reappear- 

 with usually increased intensity, though shifted slightly towards 

 the violet end of the spectrum. 2 This alkaline solution to which 

 the /inc salt has been added also shows, in marked distinction 

 to the acid solutions, a brilliant fluorescence which is most ob 

 teristic of the substance, being of a bright rosy-red colour by 

 transmitted, and bright ureeii by reflected light. 



Previously to the discovery of hydrobilirubin by Maly, a well- 

 cliaracterised urinary pigment had been isolated and described by 

 under the name of urobilin (see below), while about the 

 same time that Maly's work was carried on, a pigment had 

 obtained from teces and described, under the name of stercobilin, 

 as identical with urobilin. 3 Careful comparison by Maly of his 

 hydrobilirubin with urobilin led him to assert the complete iden- 

 tity of the two substances. This view has been n rally 



adopted, and is probably correct as a broad statement 

 There are on the other hand several observers who have expi 

 themselves against the exact identity of these subsln Their 



views are however based on comparatively slight and inooodnUTQ 

 spectroscopic differences between the natural and artiticialh 

 pared substances and on other differences, such as of the intensity 

 of their fluorescent activity, which are still less conclusive. For the 

 :it the evidence of close relationship if not of absolute iden- 

 tity sullices fully as a basis for our belief in the genetic relation- 

 ship of the bile and urinary pigments and of the ultimata 

 derivation of these from the colouring-matter of the blood 



I Miring his earlier researches on the pigments of bl" : 

 Seyler described a product resulting fn-m the reduction of li 

 tin in acid solution by the action of zinc and hydrochl.>ri 



' Maly, Cntralb.f. d. med. Wiu. 1871, 8. 849. A**al. d. rh, m IM 163 (187*) 



- Vi,. r ..r.Jt. /.! t\ /Hoi. Bd. ix. (1873), S. 160. Sec lator 'Quantitative Spectral- 

 aiialv.-e.' ls;r,, S. 99. 



3 Vanlair a. Maria*, Centralb.f d. mrd. \\'i. 1871, 8. 369. Cf. Jff<?. / 

 M5 



See MacMnnn, Clinical Chrmittr,, of I'nn*. |K'J. p. 105, or J! 

 Vol. x. H-- ill ii.--'f:irv r-furence*. But M Afatost DitqM 



see also Malv. I'tiiiger'n An-l,. \',<\ \\ .(31. 



