48 THE STOMACH. 



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 occasionally 

 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 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 materially 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 muscular 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 

 * Zoological Journal, vol. x. p. 186. 



