160 ORIGIN OF THE NITROGEN. 



pears from the preceding considerations to be derived 

 from the elements of the non-azotized food. But its 

 formation is impossible without the addition of an azo- 

 tized body, for the bile is a compound of nitrogen. All 

 varieties of bile yet examined yield, when subjected to 

 dry distillation, ammonia and other nitrogenized pro- 

 ducts. Taurine and ammonia may easily be extracted 

 from ox bile ; and the only reason why we cannot posi- 

 tively prove that the same products may be obtained 

 from the bile of other animals is this, that it is not easy 

 to procure, in the case of many of these animals, a 

 sufficient quantity of bile for the experiment. 



Now, whether the nitrogenized compound which 

 unites with the elements of starch to form bile be de- 

 rived from the food, or from the substance of the meta- 

 morphosed tissues, the conclusion, that its presence is 

 an essential condition for the secretion of bile, cannot 

 be considered doubtful. 



Since the herbivora obtain in their food only such 

 nitrogenized compounds as are identical in composition 

 with the constituents of their blood, it is at all events 

 clear, that the nitrogenized compound which enters into 

 the composition of the bile, is derived from a compound 

 of proteine. It is either formed in consequence of a 

 change which the compounds of proteine in the food 

 have undergone, or it is produced from the blood, or 

 from the substance of the tissues, by the act of their 

 metamorphosis. 



73. If the conclusion be accurate, that nitrogenized 

 compounds, whether derived from the blood or from 



