243. The same illustrious author, having repeated his observations, 1 makes the following statement respecting the incubated egg. At the end of 6 hours,... the rudiments of the carina and head of the chick were seen as a zone, 2 swimming in a colliquamentum of a leaden color which was bounded by a circle that served as a kind of dam.... At the end of 12 hours,...the carina, defined by white zones, exhibited the round capitulum or little head, and also for the first time, beyond its middle the orbicular vesicles [or sacculi] of the vertebrae, situated at intervals on either side.... In other cicatriculas thus incubated,... the carina of the chick was defined by a white zone, furnished with two processes indicating the rudiments of the head, and had the globules of the vertebrae attached to it at intervals as in the former case. After the 18th hour,... the following was the appearance of the carina: the head was defined by the white zone, as well as the tract of the spine with the sacculi of the vertebrae appended to it. Around the head and neck I more than once saw a growth of flesh, together with the rudiments of the wings.... I have often remarked, as a usual piece of nature's play, a motion present in the zones, by the coming and going of which, the areas and cavities of the carina were either enlarged or obliterated. Towards the end of the 1st day, the protuberance of the head was visible [as represented in fig. 11], and by the mutual separation of the zones in the back, a concavity or groove was formed in the carina, thereby affording a place for the spinal marrow, which bed the vesicles of the brain appended to it.... The 1st day having passed, and the incubation meanwhile proceeding, the number of protuberances about the head was increased;... a portion of the heart became visible [projecting beyond the carina in the form of a hook 3 ]; and varicose vessels were seen running forth in the umbilical area, turgid with a pale yellowish ichor. After 30 hours,... the umbilical area was covered with varicose vessels,... the color of which was at first yellowish, but became subsequently dusky red.... In the head the eyes were visible,. .. the [two] zones, united together, formed various spaces or areas, and surrounded the five vesicles of the brain, and the continuous production of the spinal marrow. At the lower extremity of the carina, a dilated angular area afforded a place for the loose extended portion of the spinal marrow [laxatae medullae]; the sacculi of the vertebrae were in their places as before. At this time the heart was clearly discernible.... I am still in doubt as to the priority of the heart or the blood.... But thus much is clear, that the stamina of the carina are observed before incubation; and afterwards, in the course of incubation, that the vertebrae, and the rudiments of the brain and spinal marrow, together with the wings and the fleshy covering, are displayed to view, while the heart, the vessels, and the blood still lie concealed. But when the little streams appear in the umbilical area, it is probable that the heart also is appended to the carina, since I could certainly detect its structure before the 30 th hour. A long interval, however, elapses, during which the heart and vessels are pervaded by an ichor, which at one time is yellow, then rust colored, and at last blood red. Whence I am inclined to my former conjecture, that the juice, the vessels, and the heart, perhaps preexist, and are manifested by degrees, as we observe in the ova of trees. 4 ... About the 36th hour of incubation, ... the cicatricula exhibited the umbilical area covered with vessels.... In the head the topmost vesicle was distended with a lead colored ichor; the other vesicles were generally smaller, and full of a pellucid fluid, and the spinal marrow continued from them was somewhat dilated inferiorly, just as we find it in the adult bird. The fleshy growth was considerable about [the upper part of the carina], and the heart projected slightly beyond [the other structures]. After 40 hours the twigs of the veins had become more evident in the cicatricula, and commencing from the extreme border, passed by prolongations into the heart, and the umbilical vessels arising from the heart, and forming an angle, gave off reticular branches, among which as yet there were not always any distinct large offsets.... In the head the usual turgid vesicles were seen, representing the brain, and the first of them looked like [a ball of] glass, and seemed to float upon the others. The sons was narrowed or contracted, and as usual surrounded the brain and spinal marrow. The eyes were placed one on each side. The heart was turgid, and pulsated in the same manner and kept the same time as I have described elsewhere.... After 2 days... the chick ... was furnished with vesicles representing the cerebrum; to these was added the cerebellum, together with the spinal marrow, which was guarded by the zones.... Near the extremity of the carina the spinal marrow was enlarged, and expanded into an oval form....The heart pulsated very distinctly.... At the end of 3 days ... the heart had grown still larger, and the blood received by the auricle from the vein, was repelled through a duct into the right ventricle, and thence [through another duct] into the left ventricle, and at length into the arteries, from which it passed into the trunk [represented in fig. 32]. From this trunk proceeded the umbilical branches, which terminated in twigs at the border, forming a reticular plexus. After the 4th day ... the blood vessels were large, and the veins, for the most part more capacious [than the arteries], occupied the border particularly with a large trunk, the blood running forth mixed with a yellowish humor....The head was conspicuously large beyond the other members. For the cristate [cerebral] vesicle, which was seen to be divided into two parts, was filled with a cinereous and somewhat concrete substance: not far from thence, in the occiput, at some little depth, the second, or the vesicle of the cerebellum, was placed, and to it was subjoined a portion of the spinal marrow. In the anterior part, at a greater depth, lay the third vesicle, and the [other] two vesicles [completing the five] formed the termination or apex in front.... Not far from the head the heart protruded out of the open thorax, ... its structure plainly consisting of muscular flesh. The umbilical vessels issued from the abdomen, and the [umbilical] artery was more capacious [than the vein], and turgid with red blood, while the vein lay below the artery, was narrower than it, and contained a yellowish humor.... At the end of the 5th day ... the head was large, and the cristate [cerebral] vesicle was as represented in the figures [37 and 38], and replete with a filamentary substance: to this vesicle was attached the cerebellum. Anteriorly the two vesicles [of the apex] were seen, with the deeper vesicle placed above them. The eyes were visible, one on each side.. The thorax was open, and the heart was situated on its outside, composed of a right and left ventricle, and of an auricle placed upon the top of the ventricles.... When the sixth day had elapsed,... the same vesicular structure as heretofore was observed in the brain: the cristate vesicle was furnished with a large vessel, and the vesicle next to it was concealed, and could not be brought into view without denuding and separating the cerebrum,.... The thorax was still open, and the heart visible; the left ventricle drawn downwards and dilated, lay upon its fellow; the auricle being superextended.... At the end of the seventh day all the parts were more clearly developed.... The cristate vesicles [of the brain] were composed externally of a fibrous substance; while their interior cavity was full of a fluid of ichor.... The cerebellum and the beginning of the spinal marrow were now solidified. The thorax was peaked or pointed, and the heart pulsated within it, covered with a slight pellicle.... The two ventricles were placed close to each other, and the left was the larger and redder, while of the auricles the right was the more capacious.... From this time till the ninth day, the viscera were rendered firmer, and the heart [now] presented its customary form.... After the ninth day ... the cristate vesicles of the brain, which terminate in the origins of the optic nerves, were smaller end more deeply seated, and inclined to the sides; and the salve circumstances were observable in the anterior vesicles. At the base of the brain, which was now nearly solidified, the following appearances presented themselves. The anterior vesicles were seen, and likewise the origins of the optic nerves, running from the cristate vesicles to the eyes. A portion of the infundibulum produced from the contiguous vesicle, gave support and continuity to the brain; and not far from this, the beginning of the spinal marrow was seen depending. On the completion of the fourteenth day,... the lungs were discernible inside the body, and of a whitish color.... On the following days, all the parts increased in firmness.... The brain, now solidified, exhibited on its upper part the roots of the optic nerves of a diminished size, the anterior ventricles, the cerebellum, and the beginning of the spinal marrow; and at the base, in addition to the parts just mentioned, the infundibulum was seen projecting." (Appendix, repetitas auctasque de Ovo Incubato Observationes continens.)
Poznámky pod čarou:
1. The treatise, De Formatione Pulli in Ovo, is dated February, 1672; the treatise, De Ovo Incubato, is dated October in the same year. The reader may consult with advantage Malpighi's Opera Posthuma, where in his Autobiography (pp. 109, 110, ed. Amsterdam, 1698) he gives a brief but interesting comment on both the above treatises.--(Tr.)
2. Or rather, "as the zone C," for Malpighi refers throughout to the numerous plates with which his treatise is illustrated. It is to be observed that the word "zone" does not in this case imply a circular figure, but is used to represent a structure of various outline encompassing the central rudiments of the chick.--(Tr.)
3. This appears to be an explanation of Swedenborg's. The heart, as Malpighi figures it, perhaps rather resembles segment of the link of a chain than a hoot.- (Tr.)
4. Respecting the ova of trees, see Malpighi, Anatome Plantarum, p. 81; ed. Lond. Fol., 1687.--(Tr.)
Such are the observations of Malpighi: but it is to be noted, that the carina is that small elongated space which contains the initiament of the head, and the thread like rudiment of the spinal marrow. This carina swims in the white zones, which latter proximately surround it, although they sometimes appear to be interrupted or discontinued at the top. But it is necessary that the reader should himself examine Malpighi's figures, and become familiar with the initial forms of the hearts of the chick, and with the singular inflections through which they pass in succession, before they coalesce into a single heart.
