TASTE OF GRANIVOROUS BIRDS. 117 



certain this point, accordingly, he rilled his balls with 

 bruised grains, introducing them as before into 

 the gizzards of various fowls ; and his conjecture 

 was partly verified, for in all the numerous trials 

 which he made he invariably found that the grains 

 were more or less dissolved in proportion to the time 

 the balls were permitted to remain in the gizzard. 



Before the process of digestion can commence, 

 therefore, the grains must be bruised, and such as 

 are not bruised before passing into the gizzard are 

 there subject to the action of the two gristly surfaces 

 already described, which in granivorous birds seem to 

 produce a rotatory motion upon the food in con- 

 sequence of one side of the cavity not corresponding 

 exactly to the other, a conformation that has been 

 well explained by Sir Everard Home. 



"In the turkey," he says, "when the external 

 surface of the gizzard is first attentively examined, 

 viewing that side which is anterior in the living bird, 

 and on which the two bellies of the muscle and 

 middle are more distinct, there being no other part to 



The gizzard of a Turkey, opened to show its grinding surfaces. 



