FOOTNOTES:
[a] See before [Book IV. Chap. 12. Note (l).]
[] Mr. Willughby saith, there are two Glands for the Secretion of the unctuous Matter in the Oyl-bag. And so they appear to be in Geese. But upon Examination, I find, that in most other Birds, (such at least as I have enquir’d into,) there is only one Gland: In which are divers little Cells, ending in two or three larger Cells, lying under the Nipple of the Oyl-bag. This Nipple is perforated, and being pressed, or drawn by the Bird’s Bill, or Head, emits the liquid Oyl, as it is in some Birds, or thicker unctuous Grease, as it is in others. The whole Oyl-bag is in its structure somewhat conformable to the Breasts of such Animals as afford Milk.
[c] In all Birds that fly much, or that have the most occasion for their Wings, it is manifest that their Wings are plac’d in the very best Part, to balance their Body in the Air, and to give as swift a Progression, as their Wings and Body are capable of: For otherwise we should perceive them to reel, and fly unsteadily; as we see them to do, if we alter their Æquipoise, by cutting the End of one of the Wings, or hanging a Weight at any of the extreme Parts of the Body. But as for such Birds as have as much occasion for Swimming as Flying, and whole Wings are therefore set a little out of the Center of the Bodies Gravity. See [Book IV. Chap. 8. Note (q).] And for such as have more occasion for Diving than Flying, and whose Legs are for that Reason set more backward, and their Wings more forward. [Chap. 4. Note (k)] of this Book.
[d] The wise Author of Nature hath afforded an Example of the great Nicety in the Formation of Birds, by the Nicely observ’d in a Part no more considerable than the Vanes of the Flag-feathers of the Wing. Among others, these two Things are observable: 1. The Edges of the exterior or narrow Vanes bend downwards, but of the interior or wider Vanes upwards; by which Means they catch, hold, and lie close to one another, when the Wing is spread; so that not one Feather may miss its full Force and Impulse upon the Air. 2. A yet lesser Nicety is observ’d, and that is, in the very sloping the Tips of the Flag-feathers: The interiour Vanes being neatly slop’d away to a Point, towards the outward Part of the Wing; and the exteriour Vanes slop’d towards the Body, at least in many Birds; and in the Middle of the Wing, the Vanes being equal, are but little slop’d. So that the Wing, whether extended or shut, is as neatly slop’d and form’d, as if constantly trimm’d with a Pair of Scissors.
[e] Since no exact Account that I know of, hath been given of the Mechanism of the Vanes, or Webs of the Feathers, my Observations may not be unacceptable. The Vane consists not of one continu’d Membrane; because if one broken, it would hardly be reparable: But of many Laminæ, which are thin, stiff, and somewhat of the Nature of a thin Quill. Towards the Shaft of the Feather, (especially in the Flag-feathers of the Wing,) those Laminæ are broad, &c. of a semicircular Form; which serve for Strength, and for the closer shutting of the Laminæ to one another, when Impulses are made upon the Air. Towards the outer Part of the Vane, those Laminæ grow slender and taper: On their under Side they are thin and smooth, but their upper outer Edge is parted into two hairy Edges, each Side having a different Sort of Hairs, laminated or broad at Bottom, and slender and bearded above the other half. I have, as well as I could, represented the uppermost Edge of one of these Laminæ in [Fig. 18.] with some of the Hairs on each Side, magnify’d with a Microscope. These bearded Bristles, or Hairs, on one Side the Laminæ, have strait Beards, as in [Fig. 19.] those on the other Side, have hook’d Beards on one Side the slender Part of the Bristle, and strait ones on the other, as in [Fig. 20.] Both these Sorts of Bristles magnify’d, (only scattering, and not close,) are represented as they grow upon the upper Edge of the Lamina s. t. in [Fig. 18.] And in the Vane, the hook’d Beards of one Lamina, always lie next the strait Beards of the next Lamina; and by that Means lock and hold each other; and by a pretty Mechanism, brace the Laminæ close to one another. And if at any Time the Vane happens to be ruffled and discompos’d, it can by this pretty easy Mechanism, be reduc’d and repair’d. Vid. [Book IV. Chap. 12. Note (m).]
[f] Pectorales Musculi Hominis flectentes humeros, parvi & parum carnosi sunt; non æquant 50am aut 70am partem omnium Musculorum Hominis. E contra in Avibus, Pectorales Musculi vastissimi sunt, & aquant, imò excedunt, & magìs pendent, quàm reliqui omnes Musculi ejusdem Avis simul sumpti. Borell. de Mot. Animal. Vol. I. Prop. 184.
Mr. Willughby having made the like Observation, hath this Reflection on it, whence, if it be possible for Man to fly, it is thought by them who have curiously weighed and considered the matter, that he would attempt such a Thing with Hopes of Success, must so contrive and adapt his Wings, that he may make use of his Legs, and not his Arms in managing them: (because the Muscles of the Legs are stronger, as he observes.) Willugh. Ornith. L. 1. c. 1. §. 19.
[g] Mr. Willughby, Ray, and many others, imagine the principal use of the Tail to be to steer, and turn the Body in the Air, as a Rudder. But Borelli hath put it beyond all doubt, that this is the least use of it, and that it is chiefly to assist the Bird in its Ascents and Descents in the Air, and to obviate the Vacillations of the Body and Wings. For as for turning to this or that Side, it is performed by the Wings and Inclination of the Body, and but very little by the help of the Tail.
[h] See Borelli ubi supr. Prop. 182, &c.
[] It is considerable in all Water-Fowl, how exactly their Legs and Feet correspond to that way of Life. For either their Legs are long, to enable them to wade in the Waters: In which case, their Legs are bare of Feathers a good way above the Knees, the more conveniently for this Purpose. Their Toes also are all abroad; and in such as bear the Name of Mudsuckers, two of the Toes are somewhat joined, that they may not easily sink in walking upon boggy Places. And as for such as are whole-footed, or whose Toes are webbed together (excepting some few) their Legs are generally short, which is the most convenient Size for Swimming. And ’tis pretty enough to see how artificially they gather up their Toes and Feet when they withdraw their Legs, or go to take their Stroke; and as artificially again extend or open their whole Foot, when they press upon, or drive themselves forward in the Waters.
[k] Some of the Characteristicks of Rapacious Birds, are, to have hooked, strong, and sharp-pointed Beaks and Talons, fitted for Rapine, and tearing of Flesh; and strong and brawny Thighs, for striking down their Prey. Willughby Ornith. L. 2. c. 1. Raii Synops. Av. Method. p. 1.
[l] Such Birds as climb, particularly those of the Wood-pecker Kind, have for this Purpose (as Mr. Willughby observes, L. 2. c. 4.) 1. Strong and musculous Thighs. 2. Short Legs and very strong. 3. Toes standing two forwards and two backwards. Their Toes also are close joined together, that they may more strongly and firmly lay hold on the Tree they climb upon. 4. All of them——have a hard stiff Tail bending also downwards, on which they lean, and so bear up themselves in climbing.
[m] Swifts and Swallows have remarkably short Legs, especially the former, and their Toes grasp any Thing very strongly. All which is useful to them in building their Nests, and other such Occasions as necessitate them to hang frequently by their Heels. But there is far greater use of this Structure of their Legs and Feet, if the Reports be true of their hanging by the Heels in great Clusters (after the manner of Bees) in Mines and Grotto’s, and on the Rocks by the Sea, all the Winter. Of which latter, I remember the late learned Dr. Fry told this Story at the University, and confirmed it to me since, viz. That an ancient Fisherman, accounted an honest Man, being near some Rocks on the Coast of Cornwal, saw at a very low Ebb, a black List of something adhering to the Rock, which when he came to examine, he found it was a great Number of Swallows, and, if I misremember not, of Swifts also, hanging by the Feet to one Another, as Bees do; which were covered commonly by the Sea-Waters, but revived in his warm Hand, and by the Fire. All this the Fisherman himself assured the Doctor of. Of this, see more, [Chap. 3. Note (d)] of this Book.
[n] In Birds that frequent not the Waters, the Wings are in the Center of Gravity, when the Bird lies along, as in Flying; but when it stands or walks, the Erection of the Body throws the Center of Gravity upon the Thighs and Feet.
CHAP. II.
Of the Head, Stomach, and other Parts of Birds.
Thus having dispatched the Parts principally concerned in the Motion of the Feather’d Tribe, let us proceed to some other Parts not yet animadverted upon. And we will begin with the Head, concerning which I have already taken notice of its Shape for making way through the Air; of the make of the Bill, for gathering Food, and other Uses; the commodious Situation of the Eye; and I might add that of the Ear too, which would be in the way, and obstruct Flight, if ’twas like that of most other Animals: Also I might say a great deal of the Conformation of the Brain, and of the Parts therein wanting, and of others added, like to what is observable in Fishes; whose Posture in the Waters resembles that of Birds in the Air[a], and both very different from Man and Beasts; and lastly, to hint at no more, I might survey the peculiar Structure of the Larynx[], the Tongue[c], the inner Ear[d], and many Matters besides; but for a Sample, I shall only insist upon the wonderful Provision in the Bill for the judging of the Food, and that is by peculiar Nerves lodged therein for that Purpose; small and less numerous in such as have the Assistance of another Sense, the Eye; but large, more numerous, and thickly branched about, to the very End of the Beak, in such as hunt for their Food out of Sight in the Waters, in Mud, or under Ground[e].
And now from the Head and Mouth, pass we to its near Ally, the Stomach, another no less notable than useful Part; whether we consider the Elegancy of its Fibres and Muscles, or its Multiplicity; one to soften and macerate, another to digest; or its Variety, suited to various Foods, some membraneous, agreeable to the frugivorous, or carnivorous Kind; same musculous and strong[f], suited to the Comminution, and grinding of Corn and Grain, and so to supply the Defect of Teeth.
And now to this Specimen of the Parts, I might add many other Things, no less curiously contriv’d, made and suited to the Occasions of these Volatiles; as particularly the Stratum and Lodgment of the Lungs[g]; the Configuration of the Breast, and its Bone, made like a Keel, for commodious Passage through the Air, to bear the large and strong Muscles, which move the Wings, and to counterpoise the Body, and support and rest it upon at roost. The Neck also might deserve our Notice, always either exactly proportion’d to the Length of the Legs, or else longer, to hunt out Food, to search in the Waters[h]; as also to counterpoise the Body in Flight[]. And lastly, I might here take Notice of the Defect of the Diaphragm, so necessary in other Animals to Respiration; and also of divers other Parts redundant, defective, or varying from other Animals. But it would be tedious to insist upon all; and therefore to the Examples already given, I would rather recommend a nice Inspection[k], of those curious Works of God, which would be manifest Demonstrations of the admirable Contrivance and Oeconomy of the Bodies of those Creatures.
From the Fabrick therefore of their Bodies, I shall pass to a Glance of one or two Things, relating to their State; and so conclude this Genus of the animal World.