THE PRINCIPLE OF VITAL AFFINITY. 329 
ganized structure. And that certain excretions are strictly of this character, 
seems to be fully ascertained, ¢. 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 from a living 
animal, when it lives 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 air, 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 ail the excretions, we have 
sufficient evidence of their being partly furnished in this way; 7. ¢., 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 will be considered afterwards. 
Thus it is certain, that part of the excretion from 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 mucous glands of the lower intestines.* When we consider that the bile 
is secreted chiefly from the venous blood of the vena portee, and that this must ne- 
cessarily be usually loaded with matters 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 large 
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 evidence, already stated, in regard to the secretion at the kidneys (although 
that evidence was not duly considered by Liresia), that a considerable part of it is 
frequently formed from matters recently absorbed into the blood from the prime 
viee, and which had never been applied to the nutrition of textures. As we know 
that the quantity of uric acid and urea, the most highly azotised of the animal 
compounds excreted, is much greater under the use of animal (7. ¢., highly azo- 
tised food) than of vegetable, while the health and even the muscular strength 
* See CarreNnTER’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. 40 
