102 
OF THE VESSELS 
1. It is not a simple diluent, but a real solvent. A 
quarter of an ounce of beef had scarcely touched the sto¬ 
mach of a crow, when the solution began. 
2. It has not the nature of saliva; it has not the nature 
of bile; but is distinct from both. By experiments out of 
the body it appears, that neither of these secretions acts 
upon the alimentary substances, in the same manner as the 
gastric juice acts. 
3. Digestion is not putrefaction; for, the digesting fluid 
resists putrefaction most pertinaciously; nay, not only 
checks its farther progress, but restores putrid substances 
4. It is not a fermentative process; for the solution 
begins at the surface, and proceeds towards the centre, 
contrary to the order in which fermentation acts and 
spreads. 
5. It is not the digestion of heat, for, the cold maw of 
a cod or sturgeon will dissolve the shells of crabs or lob¬ 
sters, harder than the sides of the stomach which contains 
them. 
In a word, animal digestion carries about it the marks of 
being a power and a process completely sui generis; dis¬ 
tinct from every other; at least from every chemical pro¬ 
cess with which we are acquainted. And the most wonder¬ 
ful thing about it is its appropriation; its subserviency to 
the particular economy of each animal. The gastric juice 
of an owl, falcon, or kite, will not touch grain; no, not 
even to finish the macerated and half-digested pulse which 
is left in the crops of the sparrows that the bird devours. 
In poultry, the trituration of the gizzard, and the gastric 
juice, conspire in the work of digestion. The gastric juice 
will not dissolve the grain whilst it is whole. Entire grains 
of barley, enclosed in tubes or spherules, are not affected 
by it. But if the same grain be by any means broken or 
ground, the gastric juice immediately lays hold of it. Here 
then is wanted, and here we find, a combination of mechan¬ 
ism and chemistry. For the preparatory grinding, the giz¬ 
zard lends its mill. And, as all mill-work should be strong, 
its structure is so, beyond that of any other muscle belonging 
to the animal. The internal coat also, or lining of the giz¬ 
zard, is, for the same purpose, hard and cartilaginous. But, 
forasmuch as this is not the sort of animal substance suited 
for the reception of glands, or for secretion, the gastric juice 
in this family, is not supplied, as in membranous stomachs, 
by the stomach itself, but by the gullet, in which the feed¬ 
ing glands are placed, and from which it trickles down into 
the stomach. 
