132 FACULTIES OF BIRDS. 



" In the American ostrich (Rhea JVtfftdM, VIEILLOT), 

 a native of a less productive soil, the gastric glands 

 are fewer in number, when compared with its size, 

 than in other birds. They only occupy a small space 

 of a circular form, on the posterior side of the cardiac 

 cavity; the smallness of their number is, however, 

 compensated by the complexity of their structure, 

 similar to that of the gastric glands in the beaver. 

 The cardiac cavity is dilated to a large size, as in the 

 cassowary, and there is a similar oblique muscular 

 valve by which it is separated from the gizzard. The 

 digastric muscle is stronger in its power, and the 

 tendons between the two bellies of the muscle are 

 beautifully distinct. The orifice leading from the 

 gizzard is so very narrow, that nothing can pass out 

 of it that has not been reduced to a small size.'' But 

 " the stones and other hard bodies which those birds 

 swallow must, from their weight, force their way into 

 the gizzard. 



" The African ostrich (Struthio camelus), an 

 inhabitant of the desert, where there are very few 

 plants, has means of economizing its food much 

 beyond the others. The gastric glands are not only 

 more complex, but more numerous ; their secretion is 

 applied to the food in the cardiac cavity, in which it 

 is retained by its gravity, is triturated by the extraneous 

 hard bodies that are swallowed, and it is then forced 

 up into the gizzard to undergo a second trituration. 

 All such substances must remain in the cardiac cavity, 

 both from its being the most depending part, and from 

 the cavity of the gizzard being too small to admit 

 their entering it. The cardiac cavity, in the instance 

 which I examined, contained stones of various sizes, 

 pieces of iron and half-pence j but between the 

 grinding surfaces of the gizzard were only broken 

 glass, beads of different colours, and hard gravel 

 mixed with the food*." 



* Home, Comp, Anat, i, 295, 



