The History of Silk, Cotton, Linen, Wool, and Other Fibrous Substances; / Including Observations on Spinning, Dyeing, and Weaving.

by Clinton G. Gilroy

In this chapter, we shall proceed to describe the Pinna of the ancients, and upon which human ingenuity has been more successfully exercised in seeking, many feet below the surface of the Ocean, for the slender filaments, the produce of an animal in almost a vegetative state of existence.

The Pinna is a bivalve[183] shell-fish, which, when full grown, is 18 inches long, and 6 wide at its broad end. It is found near the shores of South Italy, Sicily, Corsica, and Sardinia; also in the Bay of Smyrna, and in the Indian Ocean. It does not fasten itself to rocks in the same position as the muscle, but sticks its sharp end into the mud or sand, while the rest of the shell is at liberty to open in the water. In common with the muscle, it has the power of spinning a viscid matter from its body, conformably with that of the spider and caterpillar. Although the pinna is vastly larger than the muscle, its shell being sometimes found two feet long, the threads which it produces are more delicate and slender than those of the muscle, being in fineness and beauty scarcely inferior to the single filament of the comparatively minute silk-worm. Threads so delicately thin, as may readily be imagined, do not singly possess much strength; but the little power of each is made up by the aggregate of the almost infinite number which each fish puts forth to secure itself in a fixed situation, and preserve it against the rolling of the waves. The threads are, however, similar in their nature to those of the muscle, differing only in their superior fineness and greater length. These fish have, therefore, been distinguished by some naturalists, the one as the silk-worm, the other as caterpillar of the sea.

[183] An animal having two valves, or a shell consisting of two parts which open and shut.

It has been from a very remote period well known, that muscles have the power of affixing themselves either to rocks or the shells of one another, in a very firm manner; yet their method of effecting this was not understood until explained by the accurate observations of M. Réaumur, the first naturalist who ascertained that if, by any accident, the animals were torn from their hold, they possessed the power of substituting other threads for those which had been broken or injured. It was found by him, that if muscles, detached from each other, were placed in any kind of vessel and then plunged into the sea, they contrived in a very short time to fasten themselves both to the vessel’s side and one another’s shells: in this process, the extremity of each thread seemed to perform the office of a hand in seizing upon the body to which it would attach itself.

The threads issue from the shell at that part where it naturally opens, and in affixing themselves to any substance, form numerous minute cables, by which the fish steadies itself in the water. Each animal is provided with an organ, which it is difficult to designate by any name, since it performs the office of so many members, and is the only indicator of the existence of vital powers in the creature. It is by turns a tongue, an arm, and sometimes a leg. Its shape resembles that of a tongue, and is, therefore, most frequently called by that name. Whenever the fish requires to change its place, this member serves to drag its body forward, together with its cumbrous habitation: in performing a journey, the extremity of this organ, which may then be styled a leg, is fixed to some solid body, and being then contracted in length, the whole fish is necessarily drawn towards the spot where it intends to station itself; and by a repetition of these movements, the animal arrives at its destination. It is not often that the organ is put to this use, as the pinna is but little addicted to locomotion: some naturalists indeed affirm that it is always stable. The purpose to which the tongue is most frequently applied, is that of spinning the threads. Although this body is flat, and in form similar to a tongue through the greater part of its length, it becomes cylindrical about the base or root, where it is much smaller than in any other part: at this lower end are several ligatures of a muscular nature, which keep the tongue firmly fixed against the middle of the shell; four of these cords are very apparent, and serve to move the tongue in any direction according to the wants of the fish. Through the entire length of this member there runs a slit, which pierces so deeply into its surface, as almost to divide it into two longitudinal sections; this performs the office of a canal for the liquor of which the threads are formed, and serves to mould them into their proper form: the canal appears externally like a small crack, being almost covered by the flesh from either side, but internally it is much wider, and surrounded by circular fibres. The channel thus formed extends regularly from the tip to the base of the tongue, where it partakes of the form of the member and becomes cylindric, producing there a tube or pipe in which the canal terminates. The viscid substance is moulded in this tube into the shape of a cord, similar to the threads produced from it, though much thicker, and from which all the minute fibres issue and disperse. The internal surface of the tube, wherein the large cord is formed, is furnished with glands for the secretion of the peculiar substance employed in its production, and which is always in great abundance in this animal as well as in muscles.

Réaumur observed, “that although the workmanship of the land and sea animals when completed is alike, the manner of its production is very different. Spiders, caterpillars, &c., form threads of any required length, by making the viscous liquor of which the filament is formed pass through fine perforations in the organ appointed for spinning. But the way in which muscles form their thread is widely opposite; as the former resembles the work of the wire-drawer[184], so does the latter that of the founder who casts metals in a mould.” The canal of the organ destined for the muscle’s spinning is the mould in which its thread is cast, and gives to it its determinate length.

[184] This remark of M. Réaumur confirms the observations of M. H. Straus, quoted in Chapter VII. that the thread of the silk-worm is not produced by a simple emission of liquid matter through the orifices of the spinner, or that it acquires solidity at once from the drying influence of the air. Indeed, silk cannot be produced in this manner, but is secreted in the form of silk in silk vessels, and the spinning apparatus, so called, only unwinds it. Mr. Straus’s observations on this head admit of no argument. The discovery reduces all that has been heretofore written upon the subject to the character of old lumber.

Réaumur learned the manner of the muscle performing the operation of swimming by actually placing some of these fish under his constant inspection. He kept them in his apartment in a vessel filled with sea water, and distinctly saw them open their shells and put forth their tongues. They extended and contracted this organ several times, obtruding it in every direction, as if seeking the fittest place whereon to fix their threads. After repeated trials of this kind, the tongue of one was observed to remain for some time on the spot chosen, and being then drawn back with great quickness, a thread was very easily discerned, fastened to the place: this operation was again resumed, until all the threads were in sufficient number: one fibre being produced at each movement of the tongue.

The old threads were found to differ materially from those newly spun, the latter being whiter, more glossy, and transparent than the former, and it was thence discovered that it was not the office of the tongue to transfer the old threads one by one to the new spots where they were fixed, which course M. Réaumur had thought was pursued. The old threads once severed from the spot to which they had been originally fixed were seen to be useless, and that every fibre employed by the fish to secure itself in a new position was produced at the time required; and, in short, that nature had endowed some fish, as well as land insects, with the power of spinning threads, as their natural wants and instincts demanded. This fact was incontrovertibly established by cutting away, as close to the body as they could with safety be separated, the old threads, which were always replaced by others in a space of time as short as was employed by other muscles not so deprived.

“The pinna and its cancer friend” have on more than one occasion been made subjects for poetry. There is doubtless some foundation for the fact of the mutual alliance between these aquatic friends which has been thus celebrated; yet some slight coloring may have been borrowed from the regions of fancy wherewith to adorn the verse, and even the prose history of their attachment may be exposed to a similar objection.