86 



of stomach called a gizzard assumes its most 

 characteristic appearance, consisting, as it does, 

 of four distinct muscles a large hemispherical 

 pair at the sides, and a small pair at the extre- 

 mity of the cavity. It is of an almost cartilagi- 

 nous consistence, serving the animal for a kind 

 of teeth ; and such is its hardness and power of 

 resistance of injury, that it has been found cap- 

 able of breaking lancets and bending needles, 

 which have been introduced into it, without 

 itself undergoing the least injury. It appears 

 also, that birds with this kind of stomach, are 

 accustomed to increase its powers of attrition 

 as I have already noticed of the earth-worm by 

 swallowing small peebles, without which the di- 

 gestive process would be imperfect ; and it has 

 been presumed that this kind of stomach has 

 been given to herbivorous birds, in preference 

 to the plurality of stomachs which herbivorous 

 quadrupeds possess, because, while their diges- 

 tive process is not less difficult, such a plurality 

 would have been incompatible with the lightness 

 requisite for flying. Carnivorous birds have, on 

 the contrary, membranous stomachs, like car- 

 nivorous animals in general. The fluids formed 

 in the gullet and stomach of birds are, in general, 

 more copious than in those of other animals ; 

 and some birds, as the Java swallow, actually 

 construct their nests of the viscid substance 

 which, at certain seasons of the year, they pass 

 from these passages ! These nests, in appear- 

 ance something like saucers made of isinglass, 



