Page:Micrographia - or some physiological descriptions of minute bodies made by magnifying glasses with observations and inquiries thereupon.djvu/249

Rh and corrodes those tender fibres: As I have shewed in the description of a Nettle and of Cowhage.

Examining several sorts of Feathers, I took notice of these particulars in all sorts of wing-Feathers, especially in those which serv'd for the beating of the air in the action of flying.

That the outward surface of the Quill and Stem was of a very hard, stiff, and horny substance, which is obvious enough, and that the part above the Quill was fill'd with a very white and light pith, and, with the Microscope, I found this pith to be nothing else, but a kind of natural congeries of small bubbles, the films of which seem to be of the same substance with that of the Quill, that is, of a stiff transparent horny substance.

Which particular seems to me, very worthy a more serious consideration; For here we may observe Nature, as 'twere, put to its shifts, to make a substance, which shall be both light enough, and very stiff and strong, without varying from its own establish'd principles, which we may observe to be such, that very strong bodies are for the most part very heavie also, a strength of the parts usually requiring a density, and a density a gravity; and therefore should Nature have made a body so broad and so strong as a Feather, almost, any other way then what it has taken, the gravity of it must necessarily have many times exceeded this; for this pith seems to be like so many stops or cross pieces in a long optical tube, which do very much contribute to the strength of the whole, the pores of which were such, as that they seem'd not to have any communication with one another, as I have elsewhere hinted.

But the Mechanism of Nature is usually so excellent, that one and the same substance is adapted to serve for many ends. For the chief use of this, indeed, seems to be for the supply of nourishment to the downy or feathery part of the stem; for 'tis obvious enough in all sorts of Feathers, that 'tis plac'd just under the roots of the branches that grow out of either side of the quill or stalk, and is exactly shap'd according to the ranking of those branches, coming no lower into the quill, then just the beginning of the downy branches, and growing onely on the under side of of the quill where those branches do so. Now, in a ripe Feather (as one may call it) it seems difficult to conceive how the Succus nutritius should be convey'd to this pith; for it cannot, I think, be well imagin'd to pass through the substance of the quill, since, having examin'd it with the greatest diligence I was able, I could not find the least appearance of pores; but he that shall well examine an unripe or pinn'd Feather, will plainly enough perceive the Vessel for the conveyance of it to be the thin filmy pith (as 'tis call'd) which passes through the middle of the quill.

As for the make and contexture of the Down it self, it is indeed very Rh