48 
THE STOMACH. 
ally fed with dead Pigeons, it was found that the vegetable 
food, peas, wheat, and barley, which had been swallowed by 
these birds of prey, enclosed within the crops of the Pigeons, 
remained entire, being only somewhat enlarged by heat and 
moisture; though the fleshy substances, even to the very 
hones, were entirely consumed.^ 
Again, it has been observed, that this juice will not act 
upon the grain swallowed by poultry and other granivorous 
birds while it remains whole and entire.' 
This fact has been further proved by actual experiment. 
Some gastric juice was poured into a cup containing some 
whole seeds, but it produced no effect upon them till they 
were crushed. Hence it has been found, that if oats and 
barley given to horses are previously killed by heating, and 
crushed, the animal only requires half the quantity, and yet 
thrives equally well. 
In considering the real stomach or gizzard, by which name 
it will be more familiarly known, we shall find additional 
cause for admiration in the mode by which Providence, with 
reference to the food introduced, so nicely balances the grind- 
ing powers of the gizzard with the dissolving or melting 
powers of the gastric juice. This third or real stomach 
differs, like the gullet, crop, and second stomach, very mate- 
rially in different birds ; but, generally speaking, the action 
of the gizzard may be compared to that of a coffee-mill, 
grinding down the various substances introduced into a 
pulpy matter. In those which feed on flesh and insects, 
substances of no very hard texture, this stomach appears as 
a thin membranous bag in comparison with the thick mus- 
cular globes or gizzards of the grain- devouring class; and the 
reason is evident; for the animal matter on which they feed 
requires no actual grinding to reduce it, the action of the 
gastric juice being sufficient for the purpose of dissolving it; 
whereas, without the powerful working of this grinding- 
machine within its body, a fowl, for instance, without a 
gizzard, would receive no sustenance from the grains on 
Zoological Journal , vcl. x., p. 186. 
