242. MALPIGHI thus writes on the formation of the chick in the egg. "After 12 hours of incubation the ... parts became more 1 distinctly observable in the enlarged cicatricula, which rising upwards was almost horizontal. Thus the follicle 2 [or sacculus enclosing the chick] having been ruptured, the latter came in sight with a large head and two rows of vertebrae, forming the rudiments of the carina: that is to say, a series of white orbicular sacculi representing these parts, or of vesicles contiguous to each other, extended downwards, and beset the stamina of the spinal marrow; and the first rudiments of the brain were likewise obscurely visible.... After 18 hours of incubation the cicatricula presented no great alteration in structure, but occupied horizontally the apex of the egg. The chick, with a large head and oblong spine, the latter covered by the ruptured follicle, was immersed as heretofore in the colliquamentum, of which the quantity was now increased.... At the end of 24 hours,... I thought I could detect the motion of the heart, although on this point I will not be certain.... When 36 hours had elapsed,... the head was plainly seen, turgid with the usual vesicles, and also the rudiments of the wings, and the spinal marrow.... After 38 hours the chick, increasing in size, possessed a large head with three vesicles situated in it;... and was surrounded by certain coverings encompassing the whole tract of the spine, which latter was composed, as heretofore, of the round sacculi of the vertebrae. Above the origin of the wings, I now for the first time plainly saw the structure of the heart, which I had indeed sometimes thought I could detect previously; for the chick now being alive, a pulse was observable, and when this pulse ceased, a kind of dark line was at last traced.... The umbilical vessels were seen ramifying about in the circumference with varicose and reticulated twigs; hut their production as far se the heart was not yet visible; for they were obscured by the supernatant colliquamentum or thick albumen.... After 40 hours ... the head was curved; the vesicles of the brain were not so evident; the rudiments of the eyes appeared; the heart pulsated, receiving from the veins a rust colored humor, and sometimes a humor of the color of sere vine leaves. 3 For the external border of the umbilical vessels was surrounded by a thick venous circle, which at its extremities ... opened into the heart.... At first the motion of constriction observable by means of the humor driven through the veins, was evidently into the auricle; from this the expressed juice was propelled [through a narrow tube] into the ample right vertricle, by the constriction of which it was again protruded into a continuous appendage, from which there was a direct passage into the aorta. The aorta sent upwards certain considerable branches to the head, and was continued downwards in the form of a trunk, which after dividing extended as far as the extremity of the carina. Towards the middle region it gave off the umbilical branches, which spent themselves by ramifying twigs in the circumference, forming a reticular plexus, such as we always see at the extremities of the rest of the blood vessels. A very similar implication [or plexus] was observed about the venous vessel [or circle]; so that I still doubt whether it be a broad vessel, or a conglomerated reticular venous plexus.... I think, therefore, that these vesicles pulsating in succession, constitute a true heart, surrounded as they are (for I have more than once indistinctly seen it) with muscular fleshy portions that have not yet taken on opacity or redness.... It is very difficult to determine by actual observation, whether the existence of the blood precedes that of the before mentioned heart, or vice versa. For although a dark rust colored humor is frequently seen in the outer extremities of the umbilical vessels previously to the heart becoming obvious to the senses, and it may seem probable that the heart is formed out of a curved and expanded vessel, to which fleshy portions, as it were hands, are fitted externally; yet nevertheless, since at that time all the parts are so mucous, white, and pellucid, that use what glasses we may we cannot see clearly into their structure; and since, as may be remarked in insects, the structures of the most advanced periods of existence have their rudiments in the primordial state; so I still find ground to doubt respecting [the priority of the blood to] the heart. But this much certainly is visible, that the blood or sanguineous matter does not possess from the commencement all those things that are afterwards found in it. For at first we see in the vessels a species of colliquamentum conveyed by little channels towards the foetus; afterwards, by means of fermentation, a yellowish [sub-vitellinus] and rust colored humor is produced, which ultimately becomes red, and in this last state is put in circulation by the heart. Hence inasmuch as successive changes in the sanguineous matter are evidenced by the addition of color to the blood, so it may reasonably be doubted whether, in like manner, the existence of the heart is not rendered evident by motion alone, and whether the heart, although quiescent, nevertheless may not have preexisted, but in a motionless state, in consequence of its fleshy fibres not being get formed. But it seems clear that the ichor, or matter above alluded to, which afterwards becomes red, exists antecedently to the motion of the heart; but that the heart, as well as its motion, are antecedent to the rubefaction of the blood.... After the lapse of 2 days, the little sac of the colliquamentum, or the amnion, which was full of a copious dark ichor, contained the chick, the vesicles whereof filled the curving head; the sacculi of the vertebrae were still more apparent, forming longitudinal lines; and the heart, pendulous on the outside of the thorax, beat with a triple pulse; one part of it pulsating after another in succession: for the humor it received, and which was in some cases of a deeper rust color, was sent by the vein through the auricle into the ventricles, and from the ventricles into the arteries, and lastly into the umbilical vessels. I often kept the chick, and dried the yolk underneath it, and the pulsation of the heart continued without intermission for a whole day.... The veins emptied themselves by their last branches into the auricle of the heart. I was very solicitous to discover what was the first perceptible form of the heart; and so far as the blood that it contained enabled me to make it out, I have represented it in the accompanying figures (fig. 15): from which it appears that the blood is constantly carried into the auricle by the veins running from the border [of the umbilical vessels], and is expressed by the auricle through a sometimes short intermediate canal into the right ventricle; thence into the left ventricle, and thence again into the arteries, by which it is transmitted to the head on the one hand, and to the umbilical vessels on the other.... At the end of 2 days and 14 hours, the chick, increasing in size in proportion to the time, was lying prone, with curved head, in the colliquamentum. The vesicles of the brain were observed, supplied with blood vessels, together with the rudiments of the eyes; also the spinal marrow, running in a longitudinal line, and contained within the veterbrae....Certain blood vessels came from the heart, and passing towards the middle of the abdomen, produced the umbilical arteries and veins.... The blood was discharged into the auricle partly from the extreme border, and from the ascending end descending vein; the auricle then, by its pulse, protruded it into the [right] ventricle,... and this, into the next ventricle, by which it was sent at last into the aorta, to be by it distributed to the head, to the and to the umbilicus. At the end of 3 days, I found the chick lying with its body curved and turned upside down. In its head, beyond the eyes, there were five vesicles turgid with fluid, which represented the brain....The position and form of these vesicles was as follows: at the top of the head there was one of considerable size, furnished with vessels, and in shape like a hemisphere, and which, on the subsequent days, was in a manner divided into two; for which reason I am still in doubt whether it is to be regarded as one vesicle at first, or as two. In the occiput there was a kind of triangular vesicle, but the deep region [profundam partem] of the sinciput was occupied by an oval vesicle, close to which were placed the other two completing the five.... The construction of the heart was as I have here given it; for the mystery of nature, on which I before touched, was clearly resolved in the course of this day: the auricle receiving the blood from the veins pulsated with a kind of double motion, as though distinguished into two chambers, and thus the blood was propelled into the heart in a peculiar way, which requires further investigation.... At the end of the 4th day, the chick had become more distinctly visible: the brain was proportionably very large, and the five vesicles constituting it were still more conspicuous, and had come nearer together, and when lacerated, let out an ichor or fluid... The round bodies [or sacculi] representing the vertebrae were increasingly protuberant.... The course of the vena cava and aorta within the body was concealed, and the little cord of the umbilical vessels issues from the abdomen; the blood propelled through the arteries was of a deep red color, but that which returned through the veins had a yellowish hue. Inside [the body] the rudiment of the liver ... was apparent. In some instances the heart was pendulous on the outside of the thorax, and its auricles, brought nearer to it, received the blood from the veins, and supplied it to the ventricles; for the right ventricle had nor attained its usual figure, and was connected immediately to the left, which growing broader and larger (and the beginning of the aorta being at the same time retracted), by degrees assumed its own proper form. In some eggs that advanced more quickly, the cavity of the thorax was closed by a thin tunic, the heart being concealed within it, and the left ventricle hung downwards and lay upon the right. On the completion of the 6th day (see fig. 19), the chick was lying in the amnion; its head proportionably very large, and the great cerebral vesicle in a manner double, divided [from before to behind] by an oblong fissure, and affording perhaps a place for the fair, and when lacerated no fluid now escaped. The two anterior vesicles of the brain, less protuberant than before, mere somewhat obscured by the incipient growth of flesh, and the rudiment of the beak was appended to them; the vesicle [above and] between them [in the deep region of the sinciput] was almost lost to view, as was the ease also with the fifth vesicle placed in the occiput. The spinal marrow, divided into two parts, and consolidated, extended longitudinally through the carina.... The umbilical vessels issuing [from the closed abdomen] were partly sent to the thin albumen surrounding the yolk and amnion, partly into the yolk itself; and the arteries, now diminished in calibre, mere much smaller than the veins. In the abdomen the structure of the liver began more clearly to show itself....The heart, hidden within [the body], although in a mucous state, had two pulsating ventricles, from which depended the sinewy auricles, of enlarged dimensions and exerting a double motion, and also the colorless vessels.... At the end of the 7th day,... the head was large and considerable, and the brain had become more protuberant, and was contained in the usual coverings, on lacerating which, the ichor so lately fluid was found to have concreted into solid filaments, thereby forming the walls and cavities of the ventricles. Between the large eyes the beak gradually manifested itself.... The umbilical vessels, coming outwards, were elongated through the yolk and albumen. The heart, shut up within the thorax, ... was composed of two ventricles, as it mere contiguous sacculi, united together at their upper part, and with the body of the auricles placed upon the top of them; and there were two successive motions in the ventricles, and the same number in the auricles. The tubular portion, which by its pulsations propelled the blood received from the right ventricle onwards into the arteries, was drawn downwards, and now increased the capacity of the left ventricle; and both the ventricles were successively enswathed by spiral muscular fibres, connecting and encompassing them, and which constituted the fleshy portion of the heart. The auricles themselves were uneven and corrugated in consequence of the interlacing of their sinewy fibres, and constituted as it were a new miniature heart with two distinct cavities, presenting appearances analogous to what are seen in the adult state.... After the 8th day of incubation, the chick meanwhile increasing in bulk, the head still retained its relative large size, and on opening it, the cerebral mass was found to be still more solid. For the hitherto separate vesicles were now united, and constituted two eminences, containing the ventricles, the thalamus or bed of the optic nerves, the cerebellum, and the commencement of the spinal marrow.... The heart pulsated in the usual manner, and lungs of a white color were seen to have sprung up beside it. After the 12 th day, ... the structure of the lungs was discernible, the little ribs were solidified, and the muscles spread over them externally. When the 14th day had passed, the chick was already nearly perfect.... The heart was formed of united ventricles, and a number of arterial tubules, like fingers on a hand, and which previously were at a distance from the heart, were now attached to it immediately. The auricles were large and intensely red, and composed of a network or plaiting of sinewy fibres, in which meshes or interstices of different colors were perceptible." (De Formatione Pulli in Ovo.)
Poznámky pod čarou:
1. Malpighi previously describes the appearance of the parts after 6 hours of incubation.--(Tr.)
2. It is to be observed that in the following description Malpighi refers throughout to his plates, but his letters of reference are omitted by Swedenborg, the plates not being given in this work.--(Tr.)
3. Xerampelini.
