54 



ANIMAL CHEMISTRY. 



yield, when subjected to dry distillation, am- 

 monia and other nitrogenized products. 

 Taurine and ammonia may easily be ex- 

 tracted from ox bile; and the only reason 

 why we cannot positively 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 derived from the food or from 

 the substance of the metamorphosed tissues, 

 the conclusion that its presence is an essen- 

 tial 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 constitu- 

 ents of their blood, it is at all events clear, 

 that the nitrogenized compound which en- 

 ters into the composition of 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. 



74. If the conclusion be accurate, that 

 nitrogenized compounds, whether derived 

 from the blood or from the food, take a de- 

 cided share in the formation of the secre- 

 tions, and particularly of the bile, then it is 

 plain that the organism must possess the 

 power of causing foreign matters, which are 

 neither parts nor constituents of the organs 

 in which vital activity resides, to serve for 

 certain vital processes. All nitrogenized 

 substances capable of being rendered solu- 

 ble, without exception, when introduced 

 into the organs of circulation or of digestion, 

 must, if their composition be adapted for 

 such purposes, be employed by the organism 

 in the same manner as the nitrogenized pro- 

 ducts which are formed in the act of meta- 

 morphosis of tissues. 



We are acquainted with a multitude of 

 substances, which exercise a most marked 

 influence on the act of transformation as 

 well as on the nutritive process, while their 

 elements take no share in the resulting 

 changes. These are uniformly substances 

 the particles of which are in a certain state 

 of motion or decomposition, which state is 

 communicated to all such parts of the organ- 

 ism as are capable of undergoing a similar 

 transformation. 



75. Medicinal and poisonous substances 

 form a second and most extensive class of 

 compounds, the elements of which are ca- 

 pable of taking a direct or an indirect share 

 in the processes of secretion and of trans- 

 formation. These may be subdivided into 

 three great orders ; the first (which includes 

 the metallic poisons) consists of substances 

 which enter into chemical combination with 

 certain parts or constituents of the body, 

 while the vital force is insufficient to destroy 



the compounds thus formed. The second 

 division, consisting of the essential oils, 

 camphor, empyreumatic substances, and 

 antiseptics, &c., possesses the property of 

 impeding or retarding those kinds of trans- 

 formation to which certain very complex 

 organic molecules are liable; transforma- 

 tions which, when they take place out of 

 the body, are usually designated by the 

 names of fermentation and putrefaction. 



Thethird division of medicinal substances 

 is composed of bodies, the elements of which 

 take a direct share in the changes going on 

 in the animal body. When introduced into 

 the system, they augment the energy of the 

 vital activity of one or more organs ; they 

 excite morbid phenomena in the healthy 

 body. All of them produce a marked effect 

 in a comparatively small dose, and many 

 are poisonous when administered in larger 

 quantity. None of the substances in this 

 class can be said to take a decided share in 

 the nutritive process, or to be employed by 

 the organism in the production of blood ; 

 partly, because their composition is different 

 from that of blood, and partly, because the 

 proportion in which they must be given, to 

 exert their influence, is as nothing, com- 

 pared with the mass of the blood. 



These substances, when taken into the 

 circulation, alter, as is commonly said, the 

 quality of the blood, and in order that they 

 may pass from the stomach into the circu- 

 lation with their entire efficacy, we must 

 assume that their composition is not affected 

 by the organic influence of tne stomach. If 

 insoluble when given, they are rendered 

 soluble in that organ, but they are not de- 

 composed; otherwise, they would be inca- 

 pable of exerting any influence on the blood. 



76. The blood, in its normal state, pos- 

 sesses two qualities closely related to each 

 other, although we may conceive one of 

 them to be quite independent of the other. 



The blood contains, in the form of the 

 globules, the carriers, as it were, of the 

 oxygen which serves for the production of 

 certain tissues, as well as for the generation 

 of animal heat. The globules of the blood, 

 by means of the property they possess of 

 giving off the oxygen they have taken up 

 in the lungs, without losing their peculiar 

 character, determine generally the change 

 of matter in the body. 



The second quality of the blood, namely 

 the property which it possesses of becoming 

 part of an organized tissue, and its conse- 

 quent adaptation to promote the formation 

 and the growth of organs, as well as to the 

 reproduction or supply of waste in the tis- 

 sues, is owing, chiefly, to the presence of 

 dissolved fibrine and albumen. These two 

 chief constituents, which serve for nutri- 

 tion and reproduction of matter, in passing 

 through the lungs are saturated with oxygen, 

 or, at all events, absorb so much from the 

 atmosphere as entirely to lose the power of 

 extracting oxygen from the other substances 

 present in the blood. 



