244. Inasmuch as some insects have a number of hearts, and these hearts are mere vesicles, and in simplicity of structure bear a certain resemblance to the primitive heart, it will, I think, be to our purpose, to cite the description of the heart of the silk worm and butterfly as given by the same illustrious Author.
"The heart [of the silk worm]," he observes, "is placed longitudinally in the back, between the... fibres of the muscles, and the lungs [or tracheal ramifications], which latter lie on each side; and it extends from the very top of the head to the farther extremity of the body, so that when the animal is alive, an obscure longitudinal pulsation of the heart is perceived externally. This heart consists of thin membranes, which are of the same color as the fluid they enclose, being at first transparent, but afterwards becoming yellow, and losing some portion of their clearness. Whether, in addition to membranes, the heart has (as I am inclined to think) fleshy fibres for performing its contractions, is a matter beyond the information of the senses. Its figure is extraordinary. In other living creatures the heart is a conical mass formed of spiral fleshy fibres, 1 but in the silk worm and creatures of that class it is a single tube, continued from the tail to the head, and so far as I have been enabled to observe, with no dilatation or chamber at either end to originate its motions.... This tube is widened and narrowed at distinct intervals, and thus presents a number of oval dilatations continued one into the other; which ... leads me to suspect that these dilatations are so many corcula or little hearts, reciprocally assisting each other. The number of these corcula is considerable though I have not yet exactly determined it.... But it is probable...that there is one for each ring, or at any rate for each pair of lungs.... When the hearts undergo systole, the lateral extremities of each advance to its middle, and assume a thickened or prominent appearance, but they do not come close together, for the middle portion of the heart lies between them, constituting a depression, at the sides of which they form two flaps or lines. 2 But when the heart is in strong motion, these lines run together, and seem to overlap each other at its narrower part, in which case there is a rise or swelling at the middle of the heart. On the other hand, when the worm is dying, and the sides of the heaths are carried only a little and slowly towards the middle, there is then scarcely any perceptible rise in that situation. The motions of the hearts do not succeed each other at exactly the same intervals, but in silk worms as well as in other [insects] the first motion of constriction sometimes begins in the last heart placed at the tail. Thus, when the dilated portion is compressed, the thin humor contained therein is immediately extruded through the narrow portion into the next dilatation or heart, and so on; giving rise to a successive swelling, but which in a rapid diastole is too confused to be distinguishable. It becomes evident, however, when the insect is at the point of death, that the compressions are really successive, the vital humor being propelled from one heart to another, just as in other cases the blood is propelled from the auricle into the heart, and from the heart into the arteries.... Around the elongated heart, or rather around the several hearts the branches of the trachea creep and twine, so that its lesser offsets adhere closely by their terminal twigs to the membranes of the heart where they lie against the back, being there visible on account of the transparency of both the heart and its liquid. There is yet another body that besets the surface of the heart, and has offsets adhering to the latter on both sides; and furthermore, in the several grooves or incisures [between the rings], where the fleshy fibres terminate or are intercepted, this body exhibits new transverse ramifications, so given off as to present almost the appearance of four right angles; from which circumstance we may infer, that two branches are also given off on each side in this situation by the corcula or hearts themselves. There are then a kind of mucous ramifications that surround the cardiac tube, by which the muscles also are covered, and the interstices in the viscera beautifully filled up; for indeed this body or substance is so abundant, that it more than equals in bulk all the other parts of the silk worm, the whole cavity of the belly being pretty well filled with it alone. It is soft and tender, and so divided into oblong pieces or shoots, and so singularly involved, that, however carefully examined, it is impossible to discover its red structure. In order to throw light upon this point, I have found it advisable to recur to the case of other insects analogous to the silk worm. Thus in the larger caterpillars these white ramifications entirely cover the inside of the belly, and beset the viscera therein contained; and by taking a portion of them out, receiving it in water, and laying it upon a piece of glass, we shall obtain a rude notion of their course and structure. By this means we find, that they ramify in the manner of vessels, and inosculate with the branches next them similarly ramified, the whole series thus constituting a loose network. They are of an oblong shape, a little depressed, nor do they maintain a uniform breadth, but in some places are very narrow comparatively: in other parts they assume the form of leaves, then again become narrow, and ramifying like branches, inosculate and intertwine so as to form loose network.... Before the fire this globose 3 substance melts into oil and catches flame; wherefore the fatty globules contained in the reticular prolongations, as in membranous sacculi, may be likened to an omentum; and there is reason to doubt whether these are not granaries of fat, and whether by these means nature does not show the great solicitude with which she gathers add holds this oily juice. These omental prolongations are supplied by minute tracheal pipes, which strengthen them throughout their course. (Dissertatio Epistolica de Bombyce, p. 15, 17; fol., Londini, 1687.)
"In the butterfly [of the silk worm] the heart has exactly the same structure as that above described, but the external color is different, and the motion inverse, for the coats of the several hearts are now thickened, and exchange their transparency for a yellowish hue; the heart being, therefore, more conspicuous in the butterfly than in the worm and the motion of the hearts acquired during the first days of [the existence of] the aurelia [or chyrsalis], still continues; that is to say, the juice is expressed from above downwards, and propelled by successive systole. But nature is by no means so constant in the above direction but that it may be altered by even a slight cause; perhaps, indeed, nothing can be less constant: and in truth there are so many contingent anomalies in this motion of the hearts, that I may be permitted briefly to give an account of those which I have most frequently observed. I remember having remarked in the butterfly a motion of the heart (rarely met with) from below upwards; and then, very shortly afterwards, the starting places were changed, and the motion was directed from above downwards, and lasted a long time. In another case, the heart exhibited a motion towards the extremity of the body; the diastole of the upper hearts occurred but seldom, that of the lower hearts was quick and frequent, and that of the middle hearts again occurred only at long intervals: in this instance the pulse at last continued about the head alone, the other hearts being at rest, and the motion was wavy, directed from below upwards. In the butterfly likewise 4 the heart began to pulsate at the lower part, and the pulsation extended upwards towards the head; and if while this was the case the cardiac pipe was cut across, then the lower section exhibited a motion from below to above, which motion was exceedingly rapid at the bottom of the pipe, and comparatively slow and infrequent higher up; but on the other hand, the upper section pulsated the contrary way. In other examples, after making the same section, both the divided parts first contracted towards the head, and afterwards towards the tail; the contained ichor being expressed at each pulsation. In the silk worm again, just before it passed into the chrysalis state, the motion of the heart, previous to the opening of the belly, was directed from below upwards, but, after the opening, the point f departure was changed, and seventy pulsations ensued, freely traversing the entire line of the hearts: yet gradually the motion regained it, first direction from the tail to the head, and at last, on slightly drawing apart [the parietes of] the lower heart with the nails, the movement from above downwards was revived. Very often after death a variety of motions are displayed by these numerous inter communicating hearts: thus in some single one, three pulsations may take place; in that next to it, only one pulsation, or perhaps two: and the motions are various even in the same heart; for if one portion of a heart be inclined to the side, it manifests very rapid and frequent pulsations, as it were a tremor, while the rest of it, which has not been disturbed in position, beats as usual. When the insect is at the point of death, the motion does not always keep one rhythm, but sometimes is exceedingly frequent, at other times observes long intervals, and is extinguished in this manner, but reappears when the heart is wetted with water or saliva. To conclude what I have to say on this subject, I will here give an account of two observations which I was fortunate enough to make; ... the first in the heart of the caterpillar or worm commonly called pinu. In this worm, the hearts or corcula, opening one into the other, began their movements from below upwards, as I have constantly observed to be the case in all similar insects I have had to examine. Their coats mere transparent, and slightly tinted with the color of the subjacent membranes. Meanwhile these corcula were constricted in rapid succession both in an upward and downward direction, so that the contained ichor fluctuated under the stroke of these various motions; and two globules of fat, adhering to each other and slightly immersed in the humor contained within the cavity of the heart, were tossed to and fro, presenting a singular spectacle. These globules then, when the humor in which they swam was expressed by the systole of the heart, were driven from below upwards, and frequently returned with force; but when they happened to stop in the broader part of one of the hearts, the supervening systole struck them with a most rapid upward motion, and made them ascend through more than three of the other hearts; while, on the other band, as often as they happened to lodge in the narrow part, they were generally squeezed towards the tail by the compression of the systole. Not seldom during the pulsation of the hearts, these globules exhibited a whirling motion, and sometimes even rapidly fluctuated without making any considerable movement either way. The second observation I made in the chrysalis immediately after it had been formed. The motions of the hearts were directed from the head to the lower part; then from the latter to the middle; from which the fluid was sent back by propulsion the opposite way, like a hand ball; to the tail; and this game of nature lasted in this manner for no inconsiderable time, until two motions, directed to the opposite ends, burst forth from the middle, upwards and downwards: and at last a single motion was left, namely, from above to below." (Ibid., p. 38, 39.)
Poznámky pod čarou:
1. See Malplghi, Appendix de Ovo Incubato, fig. 5, 6, 8, 13, 17. (Tr.)
Hex fibris carneis in gyrum deductis.
2. Lineas paleares.
3. Malpighi previously says, in a sentence omitted by Swedenborg, that he discovered that the above substance had a globular composition.--(Tr.)
4. Malpighi as before stated that this is the case in the worm. (Tr.)
