54 MANUAL OF HISTOLOGY. 



marked degree. It is the most essential colouring matter of human 

 bile and biliary calculi, and is probably derived from haematin ; it is 

 also found in the urine of persons suffering from jaundice (Schwanda). 



BILIVERDIN, C I6 H 20 N 2 0., or (C 6 H 9 N0 2 ?) 



This is a green colouring matter, which may, under certain circumstances, 

 be obtained in a crystalline form. Its presence in fresh bile is still 

 questionable, for it is probable that it absorbs water and passes into 

 biliprasin, a coloring matter, to be presently alluded to. The relation- 

 ship to bilirubin will be easily understood from the following formula : 



C W H 18 N A + H S + = CJ3JS.O. 

 Bilirubin. Biliverdin. 



BILIFUSCIN, C 16 H 20 ]S" 2 4 . 



A non-crystallizable compound, soluble in water, containing soda or 

 ammonia, communicating to it a brown colour. It is, to all appearances, 

 of subordinate importance, and differs from bilirubin only in having one 

 more molecule of H 2 . 



BILIPRASIN, C 16 H 22 N 2 6 . 



A green amorphous pigment, soluble in alkalies with a brown colour, 

 in contradistinction to biliverdin, which, with the former, produces a green 

 solution. The formula of this pigment corresponds to that of biliverdin 

 -f one molecule of H 2 0. It occurs in biliary calculi and jaundiced 

 urine. 



BILIHUMIN, finally, is a name given by Staedeler to a dark earthy-looking 

 substance, which, however, has not yet been obtained perfectly pure, so 

 that its formula is not known. It may be obtained as the ultimate 

 decomposition product of all the four biliary pigments like melanin. 



REMARKS. It may be well at this juncture to bestow a few words upon the 

 extractive matters. Under this name we understand in zoochemistry, a set of sub- 

 stances which are partly present in the body naturally, and are partly the results of 

 chemical manipulation. They manifest no characteristic peculiarities by which they 

 may be recognised ; they do not crystallize, nor combine in regular proportions with 

 other matters, nor do they volatilise at definite temperatures. From this may be 

 perceived the difficulty of dealing with these substances, either chemically or physio- 

 logically. Our chemical acquaintance with them is therefore very incomplete. 

 Physiologically they are held to be decomposed materials, intermediate products in 

 imitative processes, although in reality there is but little proof that this is the case. 

 Several bases, acids, &c., already alluded to, have recently been separated from these 

 compounds. 



K. Cyanogen Compounds. 



38. 



As a supplement to the consideration of the azotised decomposition 

 products of the system, cyanogen, CN, and its combinations may be 

 appended here. 



Sulplwcyanogen (rhodan), CNS. This ternary radical, whose com- 

 pounds are remarkable for the beautiful red colour which they produce 

 with salts of iron, forms with H what is known as hydrosulphocyanic 



ON ) 



acid TT [ S. Unlike other compounds of cyanogen, this is generated in 



the human body, and possesses but slight poisonous properties. It occurs 

 in combination with potassium. 



