ANIMAL CHEMISTRY. 



T yV tns of the solid contents of the bile,) re- 

 tain the capacity of resorption by the ab- 

 sorbents of the small and large intestines; 

 nay, this capacity has been directly proved 

 by the administration of enemata containing 

 bile, the whole of the bile disappearing wit 1 

 the injected fluid in the rectum. 



Thus we know with certainty, that the 

 nitrogenized compounds, produced by the 

 metamorphosis of organized tissues, after 

 being separated from the arterial blood by 

 means of the kidneys, are expelled from the 

 body as Utterly incapable of further altera- 

 tion ; while the compounds, rich in carbon, 

 derived from the same source, return into 

 the system of carnivorous animals. 



The food of the carnivora is identical with 

 the chief constituents of their bodies, and 

 hence the metamorphoses which their or- 

 gans undergo must be the same as those 

 which, under the influence of the vital force, 

 take place in the matters which constitute 

 their food. 



The flesh and blood consumed as food 

 yield their carbon for the support of the re- 

 spiratory process, while its nitrogen appears 

 as uric acid, ammonia, or urea. But pre- 

 viously to these final changes, the dead flesh 

 and blood become living flesh and blood, 

 and it is, strictly speaking, the carbon of the 

 compounds formed in the metamorphoses 

 of living tissues that serves for the produc- 

 tion of animal heat. 



The food of the carnivora is converted 

 into blood, which is destined for the repro- 

 duction of organized tissues ; and by means 

 of the circulation a current of oxygen is 

 conveyed to every part of the body. The 

 globules of the blood, which ia themselves 

 can be shown to take no share in the nutri- 

 tive process, serve to transport the oxygen, 

 which they give up in their passage through 

 the capillary vessels. Here the current of 

 oxygen meets with the compounds pro- 

 duced by the transformation of the tissues, 

 and combines with their carbon to form car- 

 bonic acid, with their hydrogen to form 

 water. Every portion of these substances 

 which escapes this process of oxidation is 

 sent back into the circulation in the form of 

 the bile, which by degrees completely dis- 

 appears. 



In the carnivora the bile contains the car- 

 bon of the metamorphosed tissues; this 

 carbon disappears in the animal body, and 

 the bile likewise disappears in the vital pro- 

 cess. Its carbon and hydrogen are given 

 out through the skin and lungs as carbonic 

 cid and water ; and hence it is obvious that 

 me elements of the bile serve for respiration 

 and for the production of animal heat. 

 Every part of the food of carnivorous ani- 

 mals is capable of forming blood ; their ex- 

 crements, excluding the urine, contain only 

 inorganic substances, such as phosphate of 

 lime ; and the small quantity of organic mat- 

 ter which is found mixed with these is de- 

 rived from excretions, the use of which is 

 to promote their passage through the intes- 



tines, such as mucus. These excrements 

 contain no bile and no soda ; for water ex- 

 tracts from them no trace of anv substance 

 resembling bile, and yet bile is very soluble 

 in water, and mixes with it in every pro- 

 portion. 



Physiologists can entertain no doubt as to 

 the origin of the constituent parts of the 

 urine and of the bile. When, from the de- 

 privation of food, the stomach contracts 

 itself so as to resemble' a portion of intes- 

 tine, the gall-bladder, for want of the motion 

 which the full stomach gives to it, cannot 

 pour out the bile it contains ; hence in ani- 

 mals starved to death we find the gall-blad- 

 der distended and full. The secretion of 

 bile and urine goes on during the winter 

 sleep of hybernating animals; and we 

 know that the urine of dogs, fed for three 

 weeks exclusively on pure sugar, contains 

 as much of the most highly nitrogenize* 

 constituent, urea, as in the normal condition 

 (Marchaud. Erdmaun's Journal fur prak- 

 tische Chemie, XIV. p. 495.) 



Differences in the quantity of urea se- 

 creted in these and similar experiments are 

 explained by the condition of the animal in 

 regard to the amount of the natural motions 

 permitted. Every motion increases the 

 amount of organized tissue which under- 

 goes metamorphosis. Thus after a walk, 

 the secretion of urine in man is invariably 

 increased. 



The urine of the mammalia, of birds, and 

 of amphibia, contains uric acid or urea ; and 

 the excrements of the mollusca, and of in- 

 sects, as of cantharides and of the butterfly 

 of the silkworm, contain urate of ammonia. 

 This constant occurrence of one or two ni- 

 trogenized compounds in the excretions of 

 animals, while so great a difference exists in 

 their food, clearly proves that these com- 

 pounds proceed from one and the same 

 source. 



As little doubt can be entertained in re- 

 gard to the function of the bile in the vital 

 process. When we consider, that the ace- 

 tate of potash, given in enema, or simply 

 as a bath for the feet, renders the urine 

 strongly alkaline (Rehberger in Tiedemann's 

 Zeitschrift fur Physiologic, ii. 149,) and that 

 the change which the acetic acid here under- 

 goes cannot be conceived without the addi- 

 tion of oxygen, it is obvious, that the soluble 

 constituents of the bile, prone to change ia 

 a high degree as we know them to be, and 

 which, as already stated, cannot be employed 

 in the production of blood, must, when re- 

 :urned through the intestines into the circu- 

 .ation, in like manner yield to the influence 

 of the oxygen which they meet. The bile 

 s a compound of soda, the elements of 

 which, with the exception of the soda, dis- 

 appears in the body of a carnivorous animal. 



In the opinion of many of the most dis- 

 tinguished physiologists, the bile is intended 

 solely to be excreted ; and nothing is more 

 certain, than that a substance containing so 

 small a proportion of nitrogen cat 



