TAURINE. 181 



monia; it reddens litmus, gradually changes on exposure to the 

 air, turns yellow at 100, and at a higher temperature becomes 

 brown, and finally developes an odour resembling that of burned 

 taurine. Hence, notwithstanding these ingenious experiments of 

 Redtenbacher's, the rational constitution of taurine remains still 

 unexplained. 



Preparation. Taurine is usually obtained from ox-gall. The 

 bile, freed from its mucus by an acid, or its alcoholic extract, is 

 mixed with hydrochloric acid, and boiled for some hours till the 

 choloidic acid is completely formed from the nitrogenous acids of 

 the bile ; the acid fluid, after the removal of the choloidic acid by 

 nitration is rapidly evaporated, causing the chloride of sodium to 

 crystallise ; the acid mother-liquid is then treated with five or six 

 times its bulk of boiling alcohol, from which, as it cools, the taurine 

 separates in needles ; by recrystallisation in water it is obtained in 

 a state of purity. 



Tests. Taurine may be distinguished from every other sub- 

 stance by its crystalline form (which under the microscope is as 

 distinct in small crystals as in large ones), by its property of 

 developing sulphurous acid when heated in a glass tube open at 

 both ends, or on a platinum spatula, and finally, by the circum- 

 stance that when boiled with caustic potash, it does not form 

 a black solution, but developes ammonia, and leaves a residue 

 consisting solely of sulphurous and acetic acids in combination with 

 potash. 



Physiological Relations. 



Occurrence. Taurine has never been found isolated in the 

 healthy organism ; it appears to be contained preformed in normal 

 bile, and to occur there as an adjunct of the already described 

 cholic acid; at all events it only occurs in an isolated state in 

 decomposed or morbid bile. After the removal of the mucus, 

 the only sulphur-compound, in those animals in which the bile con- 

 tains sulphur, is taurine conjugated with cholic acid. At the 

 present time we know, by the researches of Bensch,* that sulphur 

 exists in the bile of the ox, the sheep, the fox, the bear, the dog, 

 the wolf, the goat, the domestic hen, and certain fresh-water fish; 

 and Schlieperf has found it most abundant in the bile of serpents. 

 From the bile of the pig Strecker and GundelachJ were unable to 



* Ann. d. Ch. u. Pharm. Bd. 65, S. 194-203. 

 t Ibid. Bd. GO, S. 109-112. 

 J Ibid. Bd. 62, S. 205-232. 



