taking notice, that the threads or laminae of which we have been speaking, in their natural state unite; that their union is something more than the mere apposition of loose furfaces; that they are not parted asunder without some degree of force; that nevertheess there is no glutinous Cohesion between them; that, therefore, by some mechanical means or other, they catch or clasp among themselves, thereby giving to the beard or vane its closeness and compactness of texture. Nor is this all: when two laminæ, which have been separated by accident or force, are brought together again, they immediately rcclafp: the connection, whatever it was, is perfectly recovered, and the beard of the feather becomes as smooth and firm as if nothing had happened to it. Draw your finger down the seather, which is against the grain, and you break, probably, the junction of some of the contiguous threads; draw your finger up the feather, and you restore all things to their former state. This is no common contrivance; and now for the mechanism by which it is effected. The threads or la minæ above mentioned are interlaced with one another; and the interlacing is performed

by by means of an infinite number of fibres or teeth, which the laminæ moot forth on each side, and which hook and grapple together. A friend of mine counted fifty of these fibres in one twentieth of an inch. These fibres are crooked; but curved after a different manner; for those, which proceed from the thread on the side towards the extremity of the weather, are longer, more flexible, and bent downward: whereas those which proceed from the side towards the beginning or quill end of the feather are shorter, firmer, and turn upwards. The process then which takes place is as follows. When two laminæ are pressed together, so that these long fibres are forced far enough over the short ones, their crooked parts fall into the cavity made by the crooked parts of the others: just as the latch that is fastened to a door, enters into the cavity of the catch fixed to the door post, and, there hooking itself, sajlens the door; for it is properly in this manner, that one thread of a feather is fastened to the other.

This admirable structure of the feather, which it is easy to see with the microscope, succeeds persectly for the use to which nature has designed it, which use was, not only that the laminæ might be united, but that when one

thread thread or lamina has been separated from another by some external violence, it might be reclasped with sufficient facility and expedition *.

In the ojlrich, this apparatus of crotchets and fibres, of hooks and teeth, is wanting; and we see the consequence of the want. The filaments hang loose and separate from one another, forming only a kind of down; which constitution of the feathers, however it may fit them for the flowing honours of a lady's head-dress, may be reckoned an impersection in the bird, inasmuch as wings, composed of these feathers, although they may greatly assist it in running, do not serve for flight.

But under the present division of our subject, our business with feathers is, as they are the covering of the bird. And herein a singular circumstance occurs. In the small order of birds which winter with us, from a snipe downwards, let the external colour of the seathers be what it will, their Creator has univerfally given them a bed of black down next their bodies. Black, we know, is the warmest colour: and the purpose here is, to keep in the

» The above account is taken from Memoirs fora Natural History of Animals by the Royal Academy of Paris, publisliid I/OI, p. 219, i

heat, heat, arising from the heart and circulation of the blood. It is further likewise remarkable, that this is not found in larger birds; for which there is also a reason. Small birds are much more exposed to the cold than large ones; forasmuch as they present, in proportion to their bulk, a much larger surface to the air. If a turkey was divided into a number of wrens, supposing the shape of the turkey and the wren to be similar, the surface of all the wrens would exceed the surface of the turkey, in the proportion of the length, breadth, (or, of any homologous line) of a turkey to that of a wren; which would be, perhaps, a proportion of ten to one. It was necessary therefore that small birds should be warmer clad than large ones; and this seems to be the expedient, by which that exigency is provided for.

II. In comparing different animals, I know no part of their structure which exhibits greater variety, or, in that variety, a nicer accommodation to their respective conveniency, than that which is seen in the different formations of their mouths. Whether the purpose be the reception of aliment merely, or the catching1 of prey, the picking up of seeds, the cropping of herbage, the extraction of juices, the suc

tion of liquids, the breaking and grinding of food, the taste of that food, together with the respiration of air, and in conjunction with the utterance of sound; these various offices are assigned to this one part, and, in different species, provided for, as they are wanted, by its different constitution. In the human species, forasmuch as there are hands to convey the food to the mouth, the mouth is flat, and by reason of its flatness fitted only for reception: whereas the projecting jaws, the wide rictus, the pointed teeth, of the dog and his affinities, enable them to apply their mouths to snatch and seize the objects of their pursuit. The full lips, the rough tongue, the corrugated cartilaginous palate, the broad cutting teeth, of the ox, the deer, the horse and the sheep, qualify this tribe for broujing upon their pasture; either gathering large mouthsulls at once, where the grass is long, which is the case with the ox in particular; or biting close, where it is short, which the horse and the sheep are able to do, in a degree that one could hardly expect. The retired under jaw of a swine works in the ground, after the protruding snout, like a prong or ploughshare, has made its way to the roots upon which it feeds. A 3 conformation

« VorigeDoorgaan »