The faculties of birds / [Anon].

  • James Rennie
Date:
1847
Catalogue details

Licence: Public Domain Mark

Credit: The faculties of birds / [Anon]. Source: Wellcome Collection.

    43/392 page 21
    lance, they would have been in constant danger of dashing against every intervening obstacle. “In¬ deed,’’ says Buffon, “ we may consider the celerity with which an animal moves as a just indication of the perfection of its vision. A bird, for instance, that shoots swiftly through the air, must undoubtedly see better than one which slowlv describes a tortuous */ tract. Among quadrupeds, again, the sloths have a very limited sight.” It may accordingly be inferred, that birds have more precise ideas than slow-moving caterpillars, of motion and its accompanying circum¬ stances, such as those of relative velocity, extent of country, the proportional height of eminences, and the various inequalities of hill and dale, mountain and valley. Our bird’s-eye views, of which the accurate execution is so tedious and difficult, give but a very imperfect picture of the relative inequality of the sur¬ faces which they represent; but birds can choose the proper stations, can successively traverse a field in all directions, and with one glance comprehend the whole. On the other hand, the quadruped knows only the spot where it feeds,—its valley, its moun¬ tain, or its plain ; but it has no conception of expanse of surface,-—no idea of immense distances, and no desire to push forward its excursions*. The eye of birds, it is worthy of remark, besides being peculiar in structure, is also greatly larger than in most other animals in proportion to the bulk of the head. According to M. Petit, the ball of the eye in a female eagle was, at its greatest width, an inch and a half in diameter; that of the male was three lines less ; that of an ibis, six lines ; of a stork, four times larger; that of the cassowary was four times larger than its cornea, being an inch and a half in diameter, while the cornea was only three lines * Montbeillard, Oiseaux, Prelim, f Mem. f Hist, des Animaux, 1726-36.
    digitised image 1
    digitised image 2
    digitised image 3