« PreviousContinue »
coriaceous or cartilaginous matter; and in the cranium we find the brain, which is a white substance, and very firm. At the basis of the head its oval wide mouth is placed, being above two lines long, which often discovers a white hard edge, with which it crops the fucuses and other sea-plants for his nourishment. About half an inch from the ears there are 2 horns, or antenna, like those of some testaceous animals which serve them for eyes; and these antennæ extend and contract at will, turning to either side also. The oesophagus begins at the upper and inner part of the mouth, which is a delicate long tube; near which there is another thick one, made nearly like the colon, which leads to a bag or the first stomach, which may be likened to the craw of a fowl: it is always filled with fucus mixed with sand. Sometimes this stomach is double, or at least lengthens itself considerably, and the aliment parts it, as it were, into 2 portions. After this craw or stomach we find another, which performs the same office as the gizzard of fowls. The membranes are thick, and are set with 12 stones or horny pieces, of a bright yellow colour, and as transparent as fine yellow amber, ending in points like a diamond, so that the great side or basis is set into the membrane of the gizzard as a diamond in its socket: others differ in size, having different figures, that in acting all together they may be able to break and grind the herbs the animal feeds on, as well by the strength of the muscle or gizzard which puts them into action, as by the situation of these stones assisted by grains of sand found in it, turning the whole by this trituration into a liquor. Afterwards, what was thus triturated by the power of the gizzard, passes into a 3d belly or stomach, which is covered by a purple body, resembling the parenchyma of the liver, and nearly of the same consistence: then this belly turns into a long tube, which surrounds this parenchyma, and is covered in like manner by a very fine membrane: it is full of a white liquor, like chyle, and goes to discharge itself into another reservoir, at the side of which is a yellowish gland, like a pancreas. From these 2 bodies or glands, one of which may be called hepatic, and the other pancreatic, two conduits pass out; that of the pancreas is white, the other of a blackish purple: the first conducts its chyle, condensed into a reservoir or bladder, which may be resembled to the receptaculum chyli of Pecquet, and thence passes to the fecal matter: the other conducts to a body made like the mesentery, but which is always found out of the common capacity or cavity, in which all the viscera are contained. This common capacity is very large, beginning at the head and ending at the tail of the fish it is sometimes filled with a yellowish water, and is formed by the fleshy body of the animal; which is only a membrane composed of fibres every way interwoven together, open at the top, where the organs are situated, which contain the purple juice.
There is a hollow on the back of the animal, where the canal filled with a
reddish juice passes out, carrying it to a fringed body like a mesentery; and it is there the purple juice is brought to perfection; and afterwards goes to a long sac lying under a kind of horny plate, not like the bone of the cuttle-fish, but like the bone of the sepia or little cuttle-fish, which we call le couteau. This bone or horny substance is transparent, and is of a triangular figure, or approaching the form of a bivalve shell. On the right side it is fastened by a strong cartilaginous muscle, which binds it to the body of the animal; and on the left it is open and detached, and easy to be pulled up: then it is easy to see underneath both the mesenteric body, and the tube or reservoir of the purple juice. This bone or horny plate is covered by a loose membrane, which is by no means attached to it, but capable of being filled and inflated with water or wind. The whole is covered with two membranes, which are continuations of the flesh of the fish's body: the membranes are loose, and larger than are necessary to the bone; they are wrinkled or rumpled over one another to cover the whole, and to defend the bone and viscera from all kinds of pressure; but they are ready to stretch from each other, and leave the parts destined for the purple juice uncovered. They begin a little under the neck, and extend in the female animal to the tail, which is flat; and in the male they do not go so low, but end at some distance from the tail. The females are oviparous; for eggs are found in the grand cavity, at the side of the pancreatic body.
It has already been said, that when the animal is touched he makes himself round, and throws out his purple juice, as the cuttle-fish does his ink. This juice is of a beautiful deep colour: it tinges linen, and the tincture is difficult to get out. It remains at present to try if we can collect a sufficient quantity of this juice, and to find a means of preserving the tincture; which would then be certainly of great value. When the fish is boiled, or put into spirits it shrinks. up, and loses two thirds of its size; because all the water which is in the interstices of the fibres is dissipated, and the dry fibres contract: which clearly appears from dissecting them.
LXXVIII. New Observations on the Worms that form Sponges.* By J. A. Peyssonel, M. D., F.R.S. From the French. p. 590.
The existence of the nests of corallines and lithophyta, and the mechanism of their polypi, made Dr. P. conjecture that it was the same with respect to sponges; that animals nested in the interstices of their fibres, gave them their origin and growth: but he had not yet seen nor discovered the insects, nor observed their work. Sponges appeared only as skeletons: but at length he dis
It is necessary to observe here, that Dr. Peyssonel's notion of the formation of sponges by worms is totally erroneous, and that sponges constitute a peculiar genus of Zoophytes.
covered these worms, which form sponges in the 4 following species: 1. Spongia Americana tubo similis; the tube-like sponge of Plumier. 2. Spongia Americana longissima funiculo similis; the cord-like sponge of Plumier. 3. Spongia Americana capitata et digitata; the fingered sponge of Plumier. 4. Spongia Americana favo similis; the honey-comb sponge of Plumier.
These 4 kinds differ only in form: they have the same qualities, are made by the same kinds of worm, and what may be said of the one agrees exactly with all the rest; for the same observations were made on them all.
When a fresh sponge is squeezed, the mucilage from the interstices of the fibres comes out frothy, by the mixture of the windings of its fibres: it always issues forth with sand, or little parcels of shells crushed by the sea. These fibres which consist of the twisted doubles of the sponge, form as it were a labyrinth filled with worms, which are easily crushed, and their juice is confused with the mucilage; but having carefully torn the sponges, and their gross fibres, Dr. P. discovered the living worms. These species of sponge commonly grow on sandy bottoms. At their origins is perceived as it were a nodule of sand or other matter, almost petrified, round which the worms begin to work, and round which they retire, as to their last seat or refuge; where he had seen them play, exercise themselves, and retire, by examining them with the microscope; and he had even made observations without its assistance.
The worms he found in these kinds of sponges are about one-third of a line thick, and 2 or 3 lines in length. They are so transparent, that one may discern their viscera through their coverings and substance: the blood may be seen to circulate, and all their parts to act. They have a conic figure, with a small black head furnished with two pincers: the other extremity is almost square, and much larger than the head.. On the back may be seen 2 white streaks or fillets, as if they contained the chyle: these 2 canals are parallel to each other from the head to the other extremity, where they come together. In the middle where the belly and viscera ought to be placed, a blackish matter is perceivable, which has a kind of circulation: sometimes it fills all the body of the worm, sometimes it gathers towards the head, or at the other end, and sometimes it follows the motion of the animal. This vermicular motion or progression begins at the posterior extremity, and ends at the head, which is pushed, and consequently advances forward. He kept these worms alive out of the sponge, quite detached from it more than an hour; having examined them thoroughly with a middling magnifier; for a great magnifier would be the grave of the insect.
He was surprized, after having finished his observations, when he put them near a piece of the fresh sponge, where the nests were moist, and from which he had pulled them, to see them enter into them and disappear, being lost in
the windings of the tubes. He thought to have found them again; but it was a difficult task to search for them. He crushed them, or they were themselves mashed in the tubes, which he pressed, and of which he had consequently spoiled the texture; but he could not find them; and this happened several times. These worms have no particular lodge: they crawl indifferently in the tubular labyrinth. So that without offence to Pliny and other naturalists, he does not see that it is in their power to dilate and contract the bodies of the sponges; which always remain in the same state of magnitude, without being any way sensible to the touch, or any other motion of the sea, nor to any other accident whatever, being an inanimate body; for the animal sensitive life, or whatever you will have it, belongs only to the worms, that form these bodies, and which are their dwelling places; and which, by the juice they deposit, make the sponge increase or grow, as bees, wasps, and especially the wood-lice of America, increase their nests or cells. In short, the blood or humours, which the ancients have observed, is no other than the mucilage or juice of the substance of these worms.
LXXIX. Of an Experiment, by which it appears that Salt of Steel does not enter the Lacteal Vessels. By Edward Wright, M.D. p. 594. Though iron is universally allowed to be one of the most powerful medicines now in use, yet many physicians observing that the fæces of patients who used it, either in a metallic or saline form, were tinged of a black colour, have been led to think, that in a metallic state it could not be reduced into particles fine enough to be received by the lacteal vessels; and if taken in a saline form, that it underwent a precipitation in the intestines, by which, being reduced to an earth or calx, it was in like manner rendered incapable of making its way into the blood. But the accurate experiments with which Signor Menghini has favoured the public in the Memoirs of the Bononian Academy, sufficiently prove, that the ore and filings of iron, finely levigated, enter the blood in considerable quantity; as does also the crocus, calx, or earthy part of the metal, though in less proportion than the 2 former, which were found to act with a violent stimulus on the vessels, and to have dissolved and broken the crasis of the blood of different animals, that had used them for some weeks in large doses mixed with their ordinary food. Though it must be allowed that these experiments are very curious, yet the subject seems to require a further inquiry, viz. whether iron is capable of entering the blood in a state of solution, or under a saline form: for, from the violent stimulus, as well as from the dissolution of the blood, and other symptoms brought on by the use of the ore and filings, these substances, not being properly dissolved, appear to have acted in a manner so grossly mechanical, that whatever Signor Menghini might think, very little was to be concluded
from them, with regard to the action of iron on the human body, in such cases as indicate its use, and where a rational physician would think proper to prescribe it as a medicine.
Having read Signor Menghini's memoir, Dr. W. recollected, that in the year 1753 he had, with the assistance of 2 friends, made the following experiment, in order to discover whether iron in a saline form is capable of entering the lacteals. An oz. and a half of salt of steel dissolved in a sufficient quantity of water, filtrated and mixed with about 1 lb. of bread and milk, were forced down the throat of a dog that had been kept fasting for 36 hours. An hour after he had swallowed this mixture, having secured him in a supine posture, as is usual in such experiments, they opened the abdomen, and observed the lacteal vessels, like white threads, running along the mesentery in a very beautiful manner. On slitting open part of the small guts, they there found a good deal of the mixture, which appeared frothy, but without any black colour, or the least sign of the salt being precipitated; and it struck a deep inky colour with infusion of galls. Though the white colour of the lacteals convinced them that they were full of chyle, yet as it would have been impossible to have collected a sufficient quantity of it from them, they found it necessary to open the thorax, and tie the thoracic duct a little above the receptacle, which, from the ligature, soon became turgid, the animal being alive and warm, and the chyle still continuing its course towards the thoracic duct. Having cut open the receptacle, they easily collected a sufficient quantity of chyle, and immediately mixed with it, drop by drop, infusion of galls; a very simple and easy method, by which an incredibly small quantity of salt of steel may be discovered in most liquors: but not the smallest change of colour was observed, though they were rubbed together for some time, and allowed to stand several hours. Now had there been a single atom, so to speak, of the salt in so small a portion of chyle, as that used in this experiment, which was, as near as he could guess, somewhat less than oz., it is not to be imagined that it could have failed to discover itself by this method of trial; for on adding gr. of the salt, this mixture instantly became of a bright purple: and he had found by other experiments that the smallest quantity of salt of steel shows itself as readily in the chyle by galls as in any other liquor of the same consistence. This experiment, with another observation he had made, viz. that neither the blood nor urine of patients, during the use of salt of steel, in the least change colour with galls, renders it more than probable that this salt does not enter the blood.
As the salt was found to have undergone no change in the small guts, it appeared that it is not prevented from entering the lacteals by its being decomposed or precipitated, as has been imagined; but on the contrary, that what rendered it incapable of being received by these vessels was its astringency: for the lac