THE PRINCIPLE OF VITAL AFFINITY. 329 



ganized structure. And that certain excretions are strictly of this character, 

 seems to be fully ascertained, e. g., the great excretion of oxygen from living vege- 

 tables, is merely separated from the carbon of the carbonic acid which enters them, 

 when that carbon unites with the elements of water to form starch ; and a part, 

 at least, of the carbonic acid and of the water which are thrown off fi'om a living 

 animal, when it Uves on sugar or starch, and forms oil or fat, or when it lives on 

 albuminous compounds and forms gelatin, appears, from what was formerly stated, 

 to be formed, by help of the oxygen of the aii", from such portions of the carbon 

 and hydrogen, of the starch or of the albumen, as are excluded when the new ar- 

 rangement takes place, by which fat and gelatin are formed. 



It is important to keep in mind, that, in regard to all the excretions, we have 

 sufficient evidence of their being iMrtly furnished in this way ; i. e., consisting of 

 elements which have been taken into the body, but which are either redundant, 

 or inapplicable to the nutrition of its textures ; and that these are thrown off 

 either alone, or combined only with a portion of the oxygen absorbed from the 

 air, and the influence of which on the excretions wUl be considered afterwards. 

 Thus it is certain, that part of the excretion fi-om the bowels consists merely of 

 unassimilated ingesta. It has been lately stated, with much probability, that 

 certain matters in a putrescent state, absorbed into the circulation, find a natural 

 vent in the raucous glands of the lower intestines. * When we consider that the bile 

 is secreted chiefly from the venous blood of the vena portse, and that this must ne- 

 cessarily be usually loaded with mattei'S recently absorbed by the gastric and me- 

 senteric veins, and not yet taken into the general circulation ; and when we farther 

 remember the small proportion of azote in the animal matter of bile, and the lai'ge 

 quantity of this secretion in herbivorous animals, we can have no doubt that much 

 of the matter (particularly the non-azotised matter) taken up by the veins, is brought 

 to the liver only that it may be discharged thence in the form of choleic acid. We 

 know likewise, that certain volatile matters, as alcohol or turpentine, however taken 

 into the system, are excreted by the lungs, either unchanged or united (as in the 

 case of phosphorus), with a certain portion of oxygen. And, in like manner, we 

 have CAddence, already stated, in regard to the secretion at the kidneys (although 

 that evidence was not duly considered by Liebig), that a considerable part of it is 

 frequently formed from matters recently absorbed into the blood from the primee 

 vise, and which had never been applied to the nutrition of textures. As we know 

 that the quantity of uric acid and tirea, the most highly azotised of the animal 

 compounds excreted, is much greater under the use of animal {i. e., highly azo- 

 tised food) than of vegetable, whUe the health and even the muscular strength 



* See Carpenter's Physiology, 3d edition, p. 685. This principle is probably of great impor- 

 tance in the pathology, both of hectic and typhoid fever, aud of that form of dysentery which seems to 

 result, as a specific inflammation, from certain putrescent miasmata. 



VOL. XVI. PART III. 4 O 



