136 



ON THE DIGESTIVE FUNCTION, ETC= 



possesses enables it to accomplish this purpose, and to digest coarse grass, 

 prickly shrubs, and scattered pieces of leather, with equal ease. This ani^ 

 mal is supposed to be one of the most stupid in nature, and to have no dis- 

 cernment in the choice of its food ; for it swallows stone, glass, iron, and 

 whatever else comes in its way, along with its proper sustenance. But it 

 is easy to redeem the ostrich from such a reproach, at least in the instance 

 before us : for these very articles, by their hard and indestructible property, 

 perform the office of teeth in the animal's stomach ; they enable it to tritu- 

 rate its food most minutely, and to extract its last particle of nutriment. 

 It is true that in the class of birds, or that to which the ostrich belongs, a 

 double stomach must necessarily, to a certain extent, oppose the general 

 levity by which this class is usually characterized. But the wings of the 

 ostrich are not designed for flight : they assist him in that rapidity of run- 

 ning for which he is so celebrated, and in which he exceeds all otJier ani- 

 mals, but are not designed to lift him from the earth. In reality, the 

 ostrich appears to be the connecting link between birds and quadrupeds, 

 and especially ruminant quadrupeds. In its general portrait, as well as in 

 the structure of its stomach, it has a near resemblance to the camel ; in 

 its voice, instead of a whistle, it has a grunt, hke that of the hog : in its dis- 

 position, it is as easily tamed as the horse, and like him may be employed, 

 and often has been, as a racer, though in speed it outstrips the swiftest race- 

 horse in the world. Adanson asserts, indeed, that it will do so when made 

 to carry double ; and that, when at the factory of Podore, he had two 

 ostriches carefully broken in, the strongest of which, though young, would 

 run swifter, with two negroes on his back, than a racer of the best breed. 



Yet widely different is the mechanism of the stomach in birds of flight 

 that feed on vegetables : nor could any contrivance be better adapted to 

 unite the two characters of strength and levity. Instead of the bulky and 

 complicated compartments of the membranous stomach of ruminant ani- 

 mals, we here meet with a thick, tough, n;iuscular texture, small in size, 

 but more powerful than the stoutest jaw-bone, and which is usually called 



GIZZARD. 



It consists of four distinct muscles, a large hemispherical pair at the 

 sides, and two smaller muscles at the two ends of the cavity. These mus- 

 cles are distinguished from the rest belonging to the animal, not less by 

 their colour than by their prodigious strength ; and the internal cuticle 

 with which they are covered is peculiarly callous, and often becomes quite 

 horny from pressure and friction. 



The gizzard of grazing birds, as the goose and turkey, differs in some 

 degree in the formation of its muscles from that of granivorous. They 

 have also a swell in the lower part of the esophagus, which answers the 

 purpose of a reservoir, in which the grass is retained, macerated, and 

 mixed with the secretions poured out by the glandular surfaces surround- 

 ing it, in this respect corresponding to the first and second stomachs of 

 ruminating animals, in which the grass is "prepared for mastication,"* 

 though essentially lighter.. 



In most birds, indeed, we meet with an approach towards this, in a ca- 

 vity situated above the muscular stomach, and called the crop or craw. 

 This first receives the food from the mouth, and slightly softens it by a mu- 

 cous fluid secreted from its interior ; and thu«3 prepared, a part of it is given 

 back to the young, where there are young to partake of it, and the rest is 



* HonQp, On the Gizzards of Grazing Birds, Phil. Trans, 1810, p. 183. 



