Micrographia, by Robert Hooke

Observ. xxii. Of common Sponges, and several other Spongiefibrous bodies.

A Sponge is commonly reckon'd among the Zoophyts, or Plant Animals; and the texture of it, which the Microscope discovers, seems to confirm it; for it is of a form whereof I never observ'd any other Vegetable, and indeed, it seems impossible that any should be of it, for it consists of an infinite number of small short fibres, or nervous parts, much of the same bigness, curiously jointed or contex'd together in the form of a Net, as is more plainly manifest by the little Draught which I have added, in the third Figure of the IX. Scheme, of a piece of it, which Schem. 9.
Fig. 3.
you may perceive represents a confus'd heap of the fibrous parts curiously jointed and implicated. The joints are, for the most part, where three fibres onely meet, for I have very seldom met with any that had four.

At these joints there is no one of the three that seems to be the stock whereon the other grow, but each of the fibres are, for the most part, of an equal bigness, and seem each of them to have an equal share in the joint; the fibres are all of them much about the same bigness, not smaller towards the top of the Sponge, and bigger neerer the bottom or root, as is usuall in Plants, the length of each between the joints, is very irregular and different; the distance between some two joints, being ten or twelve times more then between some others.

Nor are the joints regular, and of an equitriagonal Figure, but, for the most part, the three fibres so meet, that they compose three angles very differing all of them from one another.

The meshes likewise, and holes of this reticulated body, are not less various and irregular: some bilateral, others trilateral, and quadrilateral Figures; nay, I have observ'd some meshes to have 5, 6, 7, 8, or 9. sides, and some to have onely one, so exceeding various is the Lusus Naturæ in this body.

As to the outward appearance of this Vegetative body, they are so usuall everywhere, that I need not describe them, consisting of a soft and porous substance, representing a Lock, sometimes a fleece of Wooll; but it has besides these small microscopical pores which lie between the fibres, a multitude of round pores or holes, which, from the top of it, pierce into the body, and sometimes go quite through to the bottom.

I have observ'd many of these Sponges, to have included likewise in the midst of their fibrous contextures, pretty large friable stones, which must either have been inclos'd whil'st this Vegetable was in formation, or generated in those places after it was perfectly shap'd. The later of which seems the more improbable, because I did not find that any of these stony substances were perforated with the fibres of the Sponge.

I have never seen nor been enform'd of the true manner of the growing of Sponges on the Rock; whether they are found to increase from little to great, like Vegetables, that is, part after part, or like Animals, all parts equally growing together; or whether they be matrices or feed-baggs of any kind of Fishes, or some kind of watry Insect; or whether they are at any times more soft and tender, or of another nature and texture, which things, if I knew how, I should much desire to be informed of: but from a cursory view that I at first made with my Microscope, and some other trials, I supposed it to be some Animal substance cast out, and fastned upon the Rocks in the form of a froth, or congeries of bubbles, like that which I have often observ'd on Rosemary, and other Plants (wherein is included a little Insect) that all the little films which divide these bubbles one from another, did presently, almost after the substance began to grow a little harder, break, and leave onely the thread behind, which might be, as 'twere, the angle or thread between the bubbles, that the great holes or pores observable in these Sponges were made by the eruption of the included Heterogeneous substance (whether air, or some other body, for many other fluid bodies will do the same thing) which breaking out of the lesser, were collected into very large bubbles, and so might make their way out of the Sponge, and in their passage might leave a round cavity; and if it were large, might carry up with it the adjacent bubbles, which may be perceiv'd at the outside of the Sponge, if it be first throughly wetted, and sufferr'd to plump itself into its natural form, or be then wrung dry, and suffer'd to expand it self again, which it will freely do whil'st moist: for when it has thus plump'd it self into its natural shape and dimensions, 'tis obvious enough that the mouths of the larger holes have a kind of lip or rising round about them, but the other smaller pores have little or none. It may further be found, that each of these great pores has many other small pores below, that are united unto it, and help to constitute it, almost like so many rivulets or small streams that contribute to the maintenance of a large River. Nor from this Hypothesis would it have been difficult to explicate, how those little branches of Coral, smal Stones, shells, and the like, come to be included by these frothy bodies: But this inded was but a conjecture; and upon a more accurate enquiry into the form of it with the Microscope, it seems not to be the true origine of them; for whereas Sponges have onely three arms which join together at each knot, if they had been generated from bubbles they must have had four.

But that they are Animal Substances, the Chymical examination of them seems to manifest, they affording a volatil Salt and spirit, like Harts-Horn, as does also their great strength and toughness, and their smell when burn'd in the Fire or a Candle, which has a kind of fleshy sent, not much unlike to hair. And having since examin'd several Authors concerning them, among others; I find this account given by Bellonius, in the XI. Chap. of his 2d Book, De Aquatilibus. Spongiæ recentes, says he, à siccis longe diversæ, scopulis aquæ marinæ ad duos vel tres cubitos, nonnunquam quatuor tantum digitos immersis, ut fungi arboribus adhærent, sordido quodam succo aut mucosa potius sanie refertæ, usque adeò fœtida, ut vel eminus nauseam excitet, continetur autem iis cavernis, quas inanes in siccis & lotis Spongiis cernimus: Putris pulmonis modo nigræ conspiciuntur, verùm quæ in sublimi aquæ nascuntur multo magis opaca nigredine suffusæ sunt. Vivere quidem Spongias adhærendo Aristoteles censet: absolute vero minime: sensumque aliquem habere, vel eo argumento (inquit) credantur, quod difficillime abstrahantur, nisi clanculum agatur: Atq; ad avulsoris accessum ita contrahantur, ut eas evellere difficile sit, quod idem etiam faciunt quoties flatus tempestatésque urgent. Puto autem illis succum sordidum quem supra diximus carnis loco à natura attributum fuisse: atque meatibus latioribus tanquam intestinis aut interaneis uti. Cæterum pars ea quæ Spongiæ cautibus adhærent est tanquam folii petiolus, à quo veluti collum quoddam gracile incipit: quod deinde in latitudinem diffusum capitis globum facit. Recentibus nihil est fistulosum, hæsitantque tanquam radicibus. Superne omnes propemodum meatus concreti latent: inferne verò quaterni aut quini patent, per quos eas sugere existimamus. From which Description, they seem to be a kind of Plant-Animal that adheres to a Rock, and these small fibres or threads which we have described, seem to have been the Vessels which ('tis very probable) were very much bigger whil'st the Interstitia were fill'd (as he affirms) with a mucous, pulpy or fleshy substance; but upon the drying were shrunk into the bigness they now appear.

The texture of it is such, that I have not yet met with any other body in the world that has the like, but onely one of a larger sort of Sponge (which is preserv'd in the Museum Harveanum belonging to the most Illustrious and most learned Society of the Physicians of London) which is of a horney, or rather of a petrify'd substance. And of this indeed, the texture and make is exactly the same with common Sponges, but onely that both the holes and the fibres, or texture of it is exceedingly much bigger, for some of the holes were above an Inch and half over, and the fibres and texture of it was bigg enough to be distinguished easily with ones eye, but conspicuously with an ordinary single Microscope. And these indeed, seem'd to have been the habitation of some Animal; and examining Aristotle, I find a very consonant account hereunto, namely, that he had known a certain little Animal, call'd Pinnothera, like a Spider, to be bred in those caverns of a Sponge, from within which, by opening and closing those holes, he insnares and catches the little Fishes; and in another place he says, That 'tis very confidently reported, that there are certain Moths or Worms that reside in the cavities of a Sponge, and are there nourished: Notwithstanding all which Histories, I think it well worth the enquiring into the History and nature of a Sponge, it seeming to promise some information of the Vessels in Animal substances, which (by reason of the solidity of the interserted flesh that is not easily remov'd, without destroying also those interspers'd Vessels) are hitherto undiscover'd; whereas here in a Sponge, the Parenchyma, it seems, is but a kind of mucous gelly, which is very easily and cleerly wash'd away.

The reason that makes me imagine, that there may probably be some such texture in Animal substances, is, that examining the texture of the filaments of tann'd Leather, I find it to be much of the same nature and strength of a Sponge; and with my Microscope, I have observ'd many such joints and knobs, as I have described in Sponges, the fibres also in the hollow of several sorts of Bones, after the Marrow has been remov'd, I have found somewhat to resemble this texture, though, I confess, I never yet found any texture exactly the same, nor any for curiosity comparable to it.

The filaments of it are much smaller then those of Silk, and through the Microscope appear very neer as transparent, nay, some parts of them I have observ'd much more.

Having examin'd also several kinds of Mushroms, I finde their texture to be somewhat of this kind, that is, to consist of an infinite company of small filaments, every way contex'd and woven together, so as to make a kind of cloth, and more particularly, examining a piece of Touch-wood (which is a kind Jews-ear, or Mushrom, growing here in England also, on several sorts of Trees, such as Elders, Maples, Willows, &c. and is commonly call'd by the name of Spunk; but that we meet with to be sold in Shops, is brought from beyond Seas) I found it to be made of an exceeding delicate texture: For the substance of it feels, and looks to the naked eye, and may be stretch'd any way, exactly like a very fine piece of Chamois Leather, or wash'd Leather, but it is of somewhat a browner hew, and nothing neer so strong; but examining it with my Microscope, I found it of somewhat another make then any kind of Leather; for whereas both Chamois, and all other kinds of Leather I have yet view'd, consist of an infinite company of filaments, somewhat like bushes interwoven one within another, that is, of bigger parts or stems, as it were, and smaller branchings that grow out of them; or like a heap of Ropes ends, where each of the larger Ropes by degrees seem to split or untwist, into many smaller Cords, and each of those Cords into smaller Lines, and those Lines into Threads, &c. and these strangely intangled, or interwoven one within another: The texture of this Touch-wood seems more like that of a Lock or a Fleece of Wool, for it consists of an infinite number of small filaments, all of them, as farr as I could perceive, of the same bigness like those of a Sponge, but that the filaments of this were not a twentieth part of the bigness of those of a Sponge; and I could not so plainly perceive their joints, or their manner of interweaving, though, as farr as I was able to discern with that Microscope I had, I suppose it to have some kind of resemblance, but the joints are nothing neer so thick, nor without much trouble visible.

The filaments I could plainly enough perceive to be even, round, cylindrical, transparent bodies, and to cross each other every way, that is, there were not more seem'd to lie horizontally then perpendicularly and thwartway, so that it is somewhat difficult to conceive how they should grow in that manner. By tearing off a small piece of it, and looking on the ragged edge, I could among several of those fibres perceive small joints, that is, one of those hairs split into two, each of the same bigness with the other out of which they seem'd to grow, but having not lately had an opportunity of examining their manner of growth, I cannot positively affirm any thing of them.

But to proceed, The swelling of Sponges upon wetting, and the rising of the Water in it above the surface of the Water that it touches, are both from the same cause, of which an account is already given in the sixth Observation.

The substance of them indeed, has so many excellent properties, scarce to be met with in any other body in the world, that I have often wondered that so little use is made of it, and those onely vile and sordid; certainly, if it were well consider'd, it would afford much greater conveniencies.

That use which the Divers are said to make of it, seems, if true, very strange, but having made trial of it my self, by dipping a small piece of it in very good Sallet-oyl, and putting it in my mouth, and then keeping my mouth and nose under water, I could not find any such thing; for I was as soon out of breath as if I had had no Sponge, nor could I fetch my breath without taking in water at my mouth; but I am very apt to think, that were there a contrivance whereby the expir'd air might be forc'd to pass through a wet or oyly Sponge before it were again inspir'd, it might much cleanse, and strain away from the Air divers fuliginous and other noisome steams, and the dipping of it in certain liquors might, perhaps, so renew that property in the Air which it loses in the Lungs, by being breath'd, that one square foot of Air might last a man for respiration much longer, perhaps, then ten will now serve him of common Air.

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