THE STOMACH. 57 



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. 



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 grinding 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 this gizzard may be com- 

 pared 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 working of this 



