CHAP. IV.] 



THE BILE COLOURING MATTERS. 



313 



temperatures and in a much smaller volume of boiling water. It is 

 insoluble in absolute alcohol and in ether. 



Taurine is tasteless and its solutions are neutral to test paper. 



When boiled with HC1, or pure HNO 3 , it is not decomposed ; 

 when, however, it is boiled with a strong alkaline ley it evolves 

 acetic and sulphurous acids, but no alkaline sulphide is formed. 

 When fused with a mixture of nitre and sodium carbonate, the 

 sulphur contained in taurine is oxidised to sulphuric acid, and from 

 the amount of the latter formed the quantity of taurine may be 

 determined. 



Metallic salts added to solutions of taurine cause no precipitate. 

 If, however, moist mercuric oxide is gradually added to a boiling 

 solution of taurine a compound of taurine and mercuric oxide falls 

 which is white, almost insoluble in water and quite insoluble in 

 alcohol. 



Identification 

 of Taurine. 



This depends on the crystalline form, a study of the 

 solubility and the determination of the presence and 

 amount of sulphur which the body contains. 



SECT. 8. THE BILE COLOURING MATTERS. 



Historical Introduction. 



The colour of the bile attracted the attention of the physicians 

 of antiquity and even before the days of scientific chemistry some 

 observations, not wanting in accuracy, had been made on the changes 

 which the colour of the bile undergoes under the influence of putre- 

 faction, in the presence of air, and under the influence of acids 1 ' 2 . 



Thenard, early in the century, described a yellow colouring matter 



1 Refer to an account of the bile in Georg Heuerman's Der Arzney-Gelahrheit 

 Doctors Physiologic. Dritter Theil. Copenhagen und Leipzig, bei Friedrich Christian 

 Pelt, 1753. "Das rnerckwurdigste hiebey ist, dass selbige, wie der Herr Seger schon 

 augemercket ('De ortu et progressu bilis cysticae, 13') durch Beymischung des 

 Spiritus nitri, salis und Olei vitrioli, so besonders ihre Farbe verwandelt, denn mit 

 dem ersten wird es fast augenblicklich grim, &c." p. 786. Heuermann's book is one 

 of the most remarkable and instructive of the physiological treatises of the last century, 

 both on account of the acquaintance of its author with the literature of his time and of 

 his philosophical and original views. 



2 Haller in the chapter in which he treats of the action of acids on bile, ' Ut se 

 habeat ad acida,' has some remarks which prove conclusively that long before the time 

 of Leopold Gmelin the action of nitric acid on the biliary colouring matters had been 

 observed, although the ' play of colours ' which constitutes ' Gmelin's reaction ' had 

 not been described : " Spiritus nitri bilem efficacius cogit, ut virides et duri grumi in 



sero subsideant. Viridem fecit, quae flava fuerit Cum aqua forti alias arbusculae 



virides natae sunt ; et grumus in fundo subsedit. In aliis puto meracioris acidi 

 exemplis, bilis in coagulum amarum, viridis resinae similis, abiit, &c." Elementa 

 Physiologiae corporis humani, Auctore Alberto v. Haller. Bernae, Sumptibus Societatis 

 Typographicae, MDCCLXIV. Vide Tom. vi. p. 554. 



