Micrographia, by Robert Hooke

Observ. xxxii. Of the Figure of several sorts of Hair, and of the texture of the skin.

Viewing some of the Hairs of my Head with a very good Microscope, I took notice of these particulars:

1. That they were, for the most part, Cylindrical, some of them were somewhat Prismatical, but generally they were very neer Schem. 5.
Fig. 2.
round, such as are represented in the second Figure of the 5. Scheme, by the Cylinders EEE. nor could I find any that had sharp angules.

2. That that part which was next the top, was bigger then that which was neerer the root.

3. That they were all along from end to end transparent, though not very cleer, the end next the root appearing like a black transparent piece of Horn, the end next the top more brown, somewhat like transparent Horn.

4. That the root of the Hairs were pretty smooth, tapering inwards, almost like a Parsneb; nor could I find that it had any filaments, or any other vessels, such as the fibres of Plants.

5. That the top when split (which is common in long Hair) appear'd like the end of a stick, beaten till it be all flitter'd, there being not onely two splinters, but sometimes half a score and more.

6. That they were all, as farr as I was able to find, solid Cylindrical bodies, not pervious, like a Cane or Bulrush; nor could I find that they had any Pith, or distinction of Rind, or the like, such as I had observ'd in Horse-hairs, the Bristles of a Cat, the Indian Deer's Hair, &c.

Observations on several other sorts of Hair.

For the Brisles of a Hogg, I found them to be first a hard transparent horny substance, without the least appearance of pores or holes in it; and this I try'd with the greatest care I was able, cutting many of them with a very sharp Razor, so that they appear'd, even in the Glass, to have a pretty smooth surface, but somewhat waved by the sawing to and fro of the Razor, as is visible in the end of the Prismatical body A of the same Figure; and then making trials with causing the light to be cast on them all the various ways I could think of, that was likely to make the pores appear, if there had been any, I was not able to discover any.

Next, the Figure of the Brisles was very various, neither perfectly round, nor sharp edg'd, but Prismatical, with divers sides, and round angles, as appears in the Figure A. The bending of them in any part where they before appear'd cleer, would all flaw them, and make them look white.

The Mustacheos of a Cat (part of one of which is represented by the short Cylinder B of the same Figure) seem'd to have, all of them that I observ'd, a large pith in the middle, like the pith of an Elder, whose texture was so close, that I was not able to discover the least sign of pores; and those parts which seem to be pores, as they appear'd in one position to the light, in another I could find a manifest reflection to be cast from them.

This I instance in, to hint that it is not safe to conclude any thing to be positively this or that, though it appear never so plain and likely when look'd on with a Microscope in one posture, before the same be examin'd by placing it in several other positions.

And this I take to be the reason why many have believed and asserted the Hairs of a man's head to be hollow, and like so many small pipes perforated from end to end.

Now, though I grant that by an Analogie one may suppose them so, and from the Polonian disease one may believe them such, yet I think we have not the least encouragement to either from the Microscope, much less positively to assert them such. And perhaps the very essence of the Plica Polonica may be the hairs growing hollow, and of an unnatural constitution.

And as for the Analogie, though I am apt enough to think that the hairs of several Animals may be perforated somewhat like a Cane, or at least have a kind of pith in them, first, because they seem as 'twere a kind of Vegetable growing on an Animal, which growing, they say, remains a long while after the Animal is dead, and therefore should like other Vegetables have a pith; and secondly, because Horns and Feathers, and Porcupine's Quils, and Cats Bristles, and the long hairs of Horses, which come very neer the nature of a mans hair, seem all of them to have a kind of pith, and some of them to be porous, yet I think it not (in these cases, where we have such helps for the sense as the Microscope affords) safe concluding or building on more then we sensibly know, since we may, with examining, find that Nature does in the make of the same kind of substance, often vary her method in framing of it: Instances enough to confirm this we may find in the Horns of several creatures: as what a vast difference is there between the Horns of an Oxe, and those of some sorts of Staggs as to their shape? and even in the hairs of several creatures, we find a vast difference, as the hair of a man's head seems, as I said before, long, Cylindrical and sometime a little Prismatical, solid or impervious, and very small; the hair of an Indian Deer (a part of the middle of which is described Schem. 5.
Fig. 3.
in the third Figure of the fifth Scheme, marked with F) is bigger in compass through all the middle of it, then the Bristle of an Hogg, but the end of it is smaller then the hair of any kind of Animal (as may be seen by the Figure G) the whole belly of it, which is about two or three Inches long, looks to the eye like a thread of course Canvass, that has been newly unwreath'd, it being all wav'd or bended to and fro, much after that manner, but through the Microscope, it appears all perforated from side to side, and Spongie, like a small kind of spongy Coral, which is often found upon the English shores; but though I cut it transversly, I could not perceive that it had any pores that ran the long-way of the hair: the long hairs of Horses CC and D, seem Cylindrical and somewhat pithy; the Bristles of a Cat B, are conical and pithy: the Quils of Porcupines and Hedghoggs, being cut transversly, have a whitish pith, in the manner of a Starr, or Spur-rowel: Piggs-hair (A) is somewhat triagonal, and seems to have neither pith nor pore: And other kinds of hair have quite a differing structure and form. And therefore I think it no way agreeable to a true natural Historian, to pretend to be so sharp-sighted, as to see what a pre-conceiv'd Hypothesis tells them should be there, where another man, though perhaps as seeing, but not forestall'd, can discover no such matter.

But to proceed; I observ'd several kind of hairs that had been Dyed, and found them to be a kind of horny Cylinder, being of much about the transparency of a pretty cleer piece of Oxe horn; these appear'd quite throughout ting'd with the colours they exhibited. And 'tis likely, that those hairs being boyl'd or steep'd in those very hot ting'd liquors in the Dye-fat, And the substance of the hair being much like that of an Oxes Horn, the penetrant liquor does so far mollifie and soften the substance, that it sinks into the very center of it, and so the ting'd parts come to be mix'd and united with the very body of the hair, and do not (as some have thought) only stick on upon the outward surface. And this, the boiling of Horn will make more probable; for we shall find by that action, that the water will insinuate it self to a pretty depth within the surface of it, especially if this penetrancy of the water be much helped by the Salts that are usually mix'd with the Dying liquors. Now, whereas Silk may be dyed or ting'd into all kind of colours without boiling or dipping into hot liquors, I ghess the reason to be two-fold: First, because the filaments, or small cylinders of Silk, are abundantly smaller and finer, and so have a much less depth to be penetrated then most kind of hairs; and next, because the substance or matter of Silk, is much more like a Glew then the substance of Hair is. And that I have reason to suppose: First, because when it is spun or drawn out of the Worm, it is a perfect glutinous substance, and very easily sticks and cleaves to any adjacent body, as I have several times observed, both in Silk-worms and Spiders. Next, because that I find that water does easily dissolve and mollifie the substance again, which is evident from their manner of ordering those bottoms or pods of the Silk-worm before they are able to unwind them. It is no great wonder therefore, if those Dyes or ting'd liquors do very quickly mollifie and tinge the surfaces of so small and so glutinous a body. And we need not wonder that the colours appear so lovely in the one, and so dull in the other, if we view but the ting'd cylinders of both kinds with a good Microscope; for whereas the substance of Hair, at best, is but a dirty duskish white somewhat transparent, the filaments of Silk have a most lovely transparency and cleerness, the difference between those two being not much less then that between a piece of Horn, and a piece of Crystal; the one yielding a bright and vivid reflection from the concave side of the cylinder, that is, from the concave surface of the Air that incompasses the back-part of the cylinder; the other yielding a dull and perturb'd reflection from the several Heterogeneous parts that compose it. And this difference will be manifest enough to the eye, if you get a couple of small Cylinders, the smaller of Crystal Glass, the other of Horn, and then varnishing them over very thinly with some transparent colour, which will represent to the naked eye much the same kind of object which is represented to it from the filaments of Silk and Hair by the help of the Microscope. Now, since the threads of Silk and Serge are made up of a great number of these filaments, we may henceforth cease to wonder at the difference. From much the same reason proceeds the vivid and lovely colours of Feathers, wherein they very farr exceed the natural as well as Artificial colours of hair, of which I shall say more in its proper place.

The Teguments indeed of creatures are all of them adapted to the peculiar use and convenience of that Animal which they inwrap; and very much also for the ornament and beauty of it, as will be most evident to any one that shall attentively consider the various kinds of cloathings wherewith most creatures are by Nature invested and cover'd. Thus I have observed, that the hair or furr of those Northern white Bears that inhabite the colder Regions, is exceeding thick and warm: the like have I observ'd of the hair of a Greenland Deer, which being brought alive to London, I had the opportunity of viewing; its hair was so exceeding thick, long and soft, that I could hardly with my hand, grasp or take hold of his skin, and it seem'd so exceeding warm, as I had never met with any before. And as for the ornamentative use of them, it is most evident in a multitude of creatures, not onely for colour, as the Leopards, Cats, Rhein Deer, &c. but for the shape, as in Horses manes, Cats beards, and several other of the greater sort of terrestrial Animals, but is much more conspicuous, in the Vestments of Fishes, Birds, Insects, of which I shall by and by give some Instances.

As for the skin, the Microscope discovers as great a difference between the texture of those several kinds of Animals, as it does between their hairs; but all that I have yet taken notice of, when tann'd or dress'd, are of a Spongie nature, and seem to be constituted of an infinite company of small long fibres or hairs, which look not unlike a heap of Tow or Okum; every of which fibres seem to have been some part of a Muscle, and probably, whil'st the Animal was alive, might have its distinct function, and serve for the contraction and relaxation of the skin, and for the stretching and shrinking of it this or that way.

And indeed, without such a kind of texture as this, which is very like that of Spunk it would seem very strange, how any body so strong as the skin of an Animal usually is, and so close as it seems, whil'st the Animal is living, should be able to suffer so great an extension any ways, without at all hurting or dilacerating any part of it. But, since we are inform'd by the Microscope, that it consists of a great many small filaments, which are implicated, or intangled one within another, almost no otherwise then the hairs in a lock of Wool, or the flakes in a heap of Tow, though not altogether so loose, but the filaments are here and there twisted, as 'twere, or interwoven, and here and there they join and unite with one another, so as indeed the whole skin seems to be but one piece, we need not much wonder: And though these fibres appear not through a Microscope exactly jointed and contex'd, as in Sponge; yet, as I formerly hinted, I am apt to think, that could we find some way of discovering the texture of it, whil'st it invests the living Animal, or had some very easie way of separating the pulp or intercurrent juices, such as in all probability fill those Interstitia, without dilacerating, brusing, or otherwise spoiling the texture of it (as it seems to be very much by the ways of tanning and dressing now us'd) we might discover a much more curious texture then I have hitherto been able to find; perhaps somewhat like that of Sponges.

That of Chamoise Leather is indeed very much like that of Spunk, save onely that the filaments seem nothing neer so even and round, nor altogether so small, nor has it so curious joints as Spunk has, some of which I have lately discover'd like those of a Sponge, and perhaps all these three bodies may be of the same kind of substance, though two of them indeed are commonly accounted Vegetable (which, whether they be so or no, I shall not now dispute) But this seems common to all three, that they undergo a tanning or dressing, whereby the interspers'd juices are wasted and wash'd away before the texture of them can be discover'd.

What their way is of dressing, or curing Sponges, I confess, I cannot learn; but the way of dressing Spunk, is, by boiling it a good while in a strong Lixivium, and then beating it very well; and the manner of dressing Leather is sufficiently known.

It were indeed extremely desirable, if such a way could be found whereby the Parenchyma or flesh of the Muscles, and several other parts of the body, might be wash'd, or wafted clean away, without vitiating the form of the fibrous parts or vessells of it, for hereby the texture of thole parts, by the help of a good Microscope, might be most accurately found.

But to digress no further, we may, from this discovery of the Microscope, plainly enough understand how the skin, though it looks so close as it does, comes to give a passage to so vast a quantity of excrementitious substances, as the diligent Sanctorius has excellently observed it to do, in his medicina statica; for it seems very probable, from the texture after dressing, that there are an infinit of pores that every way pierce it, and that those pores are onely fill'd with some kind of juice, or some very pulpy soft substance, and thereby the steams may almost as easily find a passage through such a fluid vehicle as the vaporous bubbles which are generated at the bottom of a Kettle of hot water do find a passage through that fluid medium into the ambient Air.

Nor is the skin of animals only thus pervious, but even those of vegetables also seem to be the same; for otherwise I cannot conceive why, if two sprigs of Rosemary (for Instance) be taken as exactly alike in all particulars as can be, and the one be set with the bottom in a Glass of water, and the other be set just without the Glass, but in the Air onely, though you stop the lower end of that in the Air very carefully with Wax, yet shall it presently almost wither, whereas the other that seems to have a supply from the subjacent water by its small pipes, or microscopical pores, preserves its greenness for many days, and sometimes weeks.

Now, this to me, seems not likely to proceed from any other cause then the avolation of the juice through the skin; for by the Wax, all those other pores of the stem are very firmly and closely stop'd up. And from the more or less porousness of the skins or rinds of Vegetables may, perhaps, be somewhat of the reason given, why they keep longer green, or sooner wither; for we may observe by the bladdering and craking of the leaves of Bays, Holly, Laurel, &c. that their skins are very close, and do not suffer so free a passage through them of the included juices.

But of this, and of the Experiment of the Rosemary, I shall elsewhere more fully consider, seeming to me an extreme luciferous Experiment, such as seems indeed very plainly to prove the Schematism or structure of Vegetables altogether mechanical, and as necessary, that (water and warmth being apply'd to the bottom of the sprig of a Plant) some of it should be carried upwards into the stem, and thence distributed into the leaves, as that the water of the Thames covering the bottom of the Mills at the Bridge foot of London, and by the ebbing and flowing of it, passing strongly by them, should have some part of it convey'd to the Cesterns above, and thence into several houses and Cesterns up and down the City.

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Last updated Monday, March 17, 2014 at 16:42