THE STOMACH. 
57 
found dead in our severe winter, perish not from the 
inclemency of the weather, hut the deficiency of 
food; for instance, our little Wren is just as active 
and cheerful in the severest frost as the warmest 
summers day,— his supply of food, consisting of 
small insects, concealed under the hark of trees, 
never failing him. 
There is another singularity in this mysterious 
liquid, namely, the different force with which it acts 
on the various substances used for food by different 
birds. Thus the gastric juice in the stomach of those 
birds which live on flesh, acts very sparingly on 
vegetable substances. On examining the castings 
or pellets of some eagles, which had been occasion- 
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 
bones, 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 ex- 
periment. 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. 
* Zoological Journal, vol. x., p. 186. 
