. The cyclopædia of anatomy and physiology. Anatomy; Physiology; Zoology. AVES. 325 of the fertile districts of a tropical country, ve- getable food of a more easily digestible nature may be selected,and it need not be detained un- necessarily long, where a fresh supply can be so readily procured. But in the Ostrich, which dwells amidst arid sands and barren deserts, every contrivance lias been adopted in the struc- ture of the digestive apparatus to extract the whole of the nutritious matter of the food which is swallowed. In the Grallatores, where no material dif- ferences of locomotive powe
. The cyclopædia of anatomy and physiology. Anatomy; Physiology; Zoology. AVES. 325 of the fertile districts of a tropical country, ve- getable food of a more easily digestible nature may be selected,and it need not be detained un- necessarily long, where a fresh supply can be so readily procured. But in the Ostrich, which dwells amidst arid sands and barren deserts, every contrivance lias been adopted in the struc- ture of the digestive apparatus to extract the whole of the nutritious matter of the food which is swallowed. In the Grallatores, where no material dif- ferences of locomotive powers or means of obtaining food exist, the cceca present in their development a direct relation to the nature of the food, and are most developed in the Gruidic. The same holds good in the Natutores. Why the increased extent of intestinal sur- face in the above different cases should be chiefly obtained by the elongation of the cceca, will appear from the following considerations. In consequence of the stones and other foreign bodies which birds swallow, it is necessary that there should be a free passage for these through the intestinal canal, which is therefore generally short and of pretty uniform diameter. In the Omnivorous birds of the tropics,as the Hornbills, Toucans, Touracos, and Parrots, which dwell among ever-bearing fruit-trees, the rapid pas- sage of the food is not inconsistent with the extraction of a due supply of nourishment, but is compensated by the unfailing abundance of the supply. But where a greater quantity of the chyle is to be extracted from the food, and where, from the nature of the latter, a greater proportion of foreign substances is required for its tritura- tion,—while the advantages of a short intestinal tract are obtained, the chyme is at the same time prevented from being prematurely expelled by the superaddition of the two ccecal bags which communicate with the intestines by orifices that are too small to admit pebbles or undigested seeds, b
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