
THE PRINCIPLE OF VITAL AFFINITY. 319 
from the body of those parts of the ingesta which are wholly inapplicable to nu- 
trition, and for which no part of the living structure has any vital attraction. 
(3.) It is especially useful, as giving the necessary fluidity to aliments which 
must be moved to all parts of the animal frame, and applied to the nourishment 
of the organs in a state of minute subdivision, but which are often introduced 
into the system in a solid form, having been formed in one living structure, vege- 
table or animal, and applied to the purpose of nutrition in another, and often 
after a long interval of time. For this purpose, it appears certain, that various 
contrivances are employed: in many cases, the mechanical process of attrition is 
an essential preliminary ; in all cases, water is employed; in most cases, it would 
appear, especially from the observations of Lirsic, that a certain degree of inci- 
pient decomposition— speedily arrested by the action of vital affinities, but begin- 
ning on the mucous membrane, and extending to the mass of aliments—precedes 
and aids the action of the solvent; just in like manner as an incipient decompo- 
sition of starch, and formation of soluble sugar, precedes the development of ve- 
getable shoots and flowers; but especially the requisite fluidity is given by sol- 
vents, applied at different spots, and which are prepared from the blood, under 
the influence of appropriate stimuli, by a vital attraction, or selecting power, ex- 
isting at those parts. Thus, an acid liquor is prepared at the stomach and at the 
ceecum, and, with a similar intention, according to recent observations, it would 
appear, that an alkaline liquor is prepared in the salivary glands, liver, and pan- 
creas. 
(4.) The most soluble part of the ingesta, and especially the amylaceous por- 
tion, must necessarily be taken up by the veins, and carried directly to the liver 
to form bile; and as this portion, unless combined with azotised matter, is inap- 
plicable to the nutrition of any texture except the fat, we see here one ground for 
the opinion to be afterwards stated, that the animal matter of the bile is chiefly 
useful as a part of the provision for the agency of oxygen, and the maintenance 
of animal heat. 
(5.) Although we are uncertain how far transformations of the organic com- 
pounds are effected in the animal economy, as preliminary to nutrition, yet we 
_have seen that some such transformations must be admitted as a part of the 
living power of animals, for the formation of fat, of gelatin, perhaps also of 
albumen; and this process is pretty certainly commenced in the chyme, in the 
primee vice, and particularly in the organized globules there formed, to be after- 
wards carried on in the course of the circulation. 
2. In the next place, the principles laid down by Lirsia as to the distinction 
between the azotised and non-azotised classes of aliments, enable us distinctly to 
understand the law of Prout, as to the necessity of a mixture of at least two of 
the three kinds of aliment which he distinguished, the albuminous, oily, and sac- 
charine, in order to maintain life. In fact, I have no doubt we may go farther (in 
