Page:Willich, A. F. M. - The Domestic Encyclopædia (Vol. 4, 1802).djvu/477

Rh bones; but which, in the former, are almost uniformly hollow, and contain no marrow. Through these concave bones, the air communicates with the lungs, that are grown together with the back and the ribs; being connected with different cellular webs, which serve as reservoirs of air.—The flesh of birds also resembles that of the mammillary tribe; but the urine of the former, though secreted in the kidnies, is evacuated by the same canal through which their excrements are discharged: nor is their bile collected in a peculiar gall-bladder; for it is, in most instances, conveyed from the liver directly to the intestines.

The stomach of birds is either furnished with a hard membrane for grinding their food; which is the case with all such as subsist on grain; or, it has the power of dissolving their aliment, by the gastric liquor secreted in all carnivorous birds, being similar to that found in the digestive organs of men and quadrupeds; but the former possess the advantage of spontaneously vomiting hair, feathers, and other indigestible matters.

The instinct displayed by every species of birds, in constructing permanent and artificial nests, in the most appropriate spots, deserves the admiration of contemplative minds; though such proofs of providential care, and wisdom, are often regarded with indifference: this extraordinary effort to propagate their species, in the most convenient manner, is the more remarkable, as almost every genus of these creatures build habitations of a peculiar form, and with the most proper materials. Another diversity prevails in the shape, colour, and number of their eggs; the deficiency of which the female supplies, in case one or more have been robbed from her nest. Nor is the migratory instinct of many birds, in autumn, less surprizing; for, at the approach of winter, they often retire fo more genial climes, in order to avoid the hardships arising from cold weather and want of food; both being removed on their return in the spring. This wonderful propensity is evident, even in those creatures which are confined in cages; and which, at that season evince an unusual degree of anxiety and turbulence, in their captive state.

Lastly, it deserves to be noticed, that all birds are once, and many kinds of them twice, annually, subject to a change of their feathers, which is commonly termed the moulting season: this distemper arises from an obstruction in the alimentary ducts of the quills, beneath which nutritive matter accumulates, and thus forcibly propels the feathers. At this period, birds appear diseased, or in a state similar to that proceeding from the obstructed oleaginous gland, which is situated above their fundament; and which secretes an oily fluid designed to lubricate their downy coat; thus enabling them to resist moisture.

Without these charming warblers, the most beautiful and fertile regions of the earth would exhibit a silent, and often dismal, scenery. How much, therefore, are mankind indebted to these airy companions of their journey through life!—Male birds greatly surpass the females in beauty, song, and size; excepting in those of prey; where, in general, the contrary prevails. Many species of the winged tribe are so remarkably docile, as to tate