Part 3

59. That the embryo probably lives in utero in virtue of its own life-principle, even through the entire period of gestation, (51, 56, and 58,) is rendered probable by many facts related by unimpeached authorities, which go to prove that when the whole intact Ovum has been expelled at an advanced period of gestation, or at the natural termination of that period, the fœtus has continued to live, and the circulation of the blood has not ceased for an instant during a space of time of from nine minutes to a quarter of an hour. (Roederer, Wrisberg, Osiander, and Meckel, who repeated the experiments of the latter.) It has been asserted by a venerated authority that in an intact Ovum, expelled at seven months, the fœtus lived upwards of an hour. (Harvey.) The truth of this assertion is confirmed by very recent observers (Green, Velpeau, Gardien, Dr. Campbell)[9]. I once destroyed a female cat by prussic acid near the time of parturition; and having removed from the horns of the uterus the entire Ova, with their beautiful annular placentæ, while the fœtus in each of them was still perfectly lively, and could distinctly be seen, through the membranes, to move, I found that at the end of thirty-five, forty, and even forty-two minutes, some of them were still alive, the Ova remaining entire all the time, and upon the table[10].

60. When the Ovulum has made good its fastening to the adventitious lining of the womb (decidua), the circulation of the blood in it is as yet imperfect. The Ovulum does not—cannot—receive the blood of the mother. How could such a gossamer-like being, organized as the Ovulum has been proved to be, during the first days after fecundation, be made a part of so impetuous a torrent as the circulation of the blood of the mother, without instant destruction to the produce of conception? No. The blood of the embryo is first formed within itself. (Prevost, Home, Magendie, Adelon, Serres, Rolando.)

61. The newly-engendered being passes through two striking metamorphoses previously to the enjoyment of its extra-uterine life. These are the Embryonic and the Fœtal states. The latter succeeds immediately to the former; beginning at the moment when the new being is grafted on the maternal womb, and continuing until its expulsion from thence at the full period of gestation. It follows, therefore, that the Embryonic or former state is that in which the new being is as yet, without any direct or indirect communication with the mother, and still less so with external objects. This state persists for about two weeks after fecundation, during which the Embryo continues to derive its nourishment from the cortical membrane of the Ovum. (Boer, Soemmering, Plagge, myself.)

62. The growth and progress of the Embryo or Fœtus follow a very irregular march. Up to the second month the increase is somewhat slow—it is accelerated during the third—it slackens again at the fourth and fifth months—between which and the last month the increase is more rapid, until it has acquired its proper maturity. (Autenrieth, Soemmering.)[11]

63. The Embryo may be perceived, with the naked eye, at the fourteenth day after conception. It measures then 1–12th of an inch in length. (Dr. Pockels.) On the third week, it is 1–10th of an inch long. It is as large as a house-fly at four weeks, and as a horse-fly at six weeks. At two months it weighs twenty grains, and is one inch long. It weighs an ounce and a half at three months, and measures three inches; between which time and the sixth month it increases in dimensions from three to nine inches, and in weight from one ounce and a half to one pound. The relative weights of augmentation of length for the seventh, eighth, and ninth months stand thus:—from two to four pounds, and twelve inches; from four to five pounds, and seventeen inches: from five to eight pounds and twenty-two inches. (Averages of minute and accurate observations made by Autenrieth, Soemmering, Bichat, Pockels, Carus, &c.—confirmed by my own observations made on several early ova, and many fœtuses examined in the course of seventeen years obstetrical practice.)

64. Towards the end of the first month it is easy to distinguish the head of the fœtus, which has the appearance of a vesicle composed of thin membranes, and is as large as the rest of the body. The latter is straight—and there is in one part of the head a black dot, marking the spot for the eyes. (Plate I. fig. 5.)[12] But it is during the second month that the various parts of the face, as well as the superior and inferior extremities, become visibly delineated in the fœtus. The eyes are indicated by two black spots of considerable size, compared to the volume of the fœtus. The eyelids are not spread over them until the tenth week, at which time the external concha of the ear, as well as the profile form of the nose, become properly defined. At this same period we find the mouth, which was at first a simple opening of no mean size, becoming more distinctly delineated, owing to the formation of the lips. These soon approach each other, leaving a simple transversal slit or depression between them. (Plate II. fig. 11 and 12.)

65. The extremities appear in the form of globular tubercles at first; the superior preceding the inferior by a short period of time. Until between the third and fourth month, the lower are smaller than the superior extremities. Even at the latter month they are shorter than the projection of the os coccygis. The parts of reproduction may then be distinctly seen. In the male as well as in the female, these parts are exceedingly prominent. (Plate V. fig. 18 and 19.) But the difference of the sexes may be deduced from other circumstances besides the sexual organs. Such as the particular structure of the thorax and abdomen, the form of the head, the extremities, and the dorsal spine. (Autenrieth, Soemmering, Meckel, Velpeau.)

66. The external organs of the fœtus are all well defined at the end of the fourth month. The abdomen is fully covered in; the intestines are no longer visible. By the sixth month the fœtus is perfect in its shape and formation. In the seventh, eighth, and ninth months, its successive development is limited to mere size, volume, or amplitude, and a proportionate increase in weight. It is well to keep in mind, that although the growth of the various parts of the fœtus bears a proportion to the general development of its body, that part of the body which is above the navel, measures in length more than the part below it, until the full and complete period of gestation, when the navel marks the precise middle of the length of the fœtus. This circumstance assists us materially in forming our opinion respecting the age of any fœtus, either as a matter of curiosity, or as a guide in questions of forensic medicine. (Foderé, Chaussier.)

67. It was supposed, until within the last fifteen years, that the nervous system was the first to be formed in the human embryo; but recent discoveries have proved that the vascular system has precedence of the former. The nerves invariably appear after the arteries which they are intended to accompany. The spinal marrow appears before the brain, and the latter before the cerebellum, and accordingly it is found that the arteries of the spinal marrow shew themselves before those of the brain, and the arteries of the brain become manifest before those of the cerebellum. In this respect the organogenesy of the human fœtus is analogous to that of birds. (Serres, Desmoulins, Adelon.)[13]

68. The blood is formed independently of the heart, and appears at two distinct points from it, and acquires a motion independently of it. (Prevost, Dumas, Baer.) The veins are formed first—next, the heart—lastly, the arteries, &c. (French Physiologists.) The arteries are, by an Italian physiologist, said to be the first to appear. (Rolando.)[14]

69. The nervous system is not developed, beginning at the centre and proceeding towards the circumference of the embryo, but the reverse. Thus the lateral nerves of the head, trunk, and pelvis, are already formed, when the cerebro-spinal system is yet in a liquid state. It follows hence that those nerves cannot be considered (as it has all along been supposed) in the light of emanations from, but as distinct bodies proceeding to, that particular portion of the nervous system. (Serres.)

70. Of the apparatus for digestion, the intestinal canal is the first to appear. It consists, during the first days of its formation, of an open gutter, extending the whole length of the embryo, placed before the vertebral column, and gently curved like a canoe. It is in communication with the _vesicula umbilicalis_, or intestinal vesicle. (Wolf, Meckel, Oken, Baer.) The gutter, without losing altogether its communication with that vesicle or chamber during the first ten or twelve weeks, becomes closed at last, and extends, lengthens, and expands in a variety of ways. One of its extremities, the mouth, appears between the fourth and fifth week. It is open on the sixth. The other extremity, the anus, opens on the seventh week. About the ninth week, the outlines of a stomach are visible. (Meckel., Adelon, Velpeau.)[15]

71. The VESICULA UMBILICALIS (intestinal vesicle) corresponds to the vitelline sac of birds. The discovery is due to Bojanus. In the human embryo it measures about half an inch in diameter. It is situated immediately against the anterior surface of the embryo (Lobstein); but it gets further from it at the end of the first month, when it is found on the outside of the sheath of the cord. (Meckel.) It is composed of a granular membrane of considerable tenacity. It contains a whitish liquid, which gradually diminishes—becomes thicker, and ultimately, hardened; while the vesicle itself withers, and becomes opaque. It receives the blood vessels called omphalo-mesenteric. (Pockels.) It disappears generally about the third month. (Meckel.) It has been observed, though extremely rarely, at the full period of gestation—placed at a short distance from the insertion of the cord into the placenta, but not larger than when seen at between two and three months. (Hunter, Meckel.) It is connected, as stated before, by a short neck, and by vessels, with the smaller intestines at the termination of the ileum (Meckel)—or at the cæcum, which is, in reality, the representative of the vesicula vitellaria drawn into the abdomen as in birds. (Oken.)

72. At the lower end of the anal intestines, there projects another vesicle or sac, to which the name of Allantoid has been given. It exists in birds—in all the mammalia—and in the human embryo. In the latter it appears about the fourth week, and by the sixth week it has almost disappeared. Its existence is therefore but short, while the size it attains is always trifling. Not so with the mammalia, in which it acquires great amplitude. The communication of this sac with the bladder, by a canal called the urachus, and which canal is found impervious after the first three or four months of gestation, is admitted by all observers. (Meckel, Baer, Dutrochet.)

73. The umbilical cord or navel string, in man, has been found to spring from a vesicle to which the discoverer has given the name of Erythroid. (Dr. Pockels.) This vesicle had been before observed in the mammalia. (Oken.) The cord appears at the end of the third week. (Pockels.) It then consists of a vein and two arteries, the urachus, a species of gelatine of a ropy nature, called the _gelatine of Wharton_, a portion of the intestinal canal, (larger in proportion as the embryo is younger,) the vesicula umbilicalis, in part, and the omphalo-mesenteric vessels, the whole enveloped by a sheath proceeding from the involucra of the ovum already described. The last three constituent elements of the cord, however, become obliterated or disappear after the third or fourth month of gestation—the others remain permanent throughout that period.

74. The umbilical vein and the arteries are spirally twisted together and in the majority of cases they are so from left to right. (Hunter.) The former contrivance is evidently intended for the purpose of giving the greatest possible extension of tubular passage for the blood compatible with the smallest increase in the length of the cord. The cord which is very short at five or six weeks, becomes at the conclusion of gestation from one foot six to two feet long. (Chaussier.)

75. The umbilical arteries, two in number, are a continuation of the primitive iliac arteries; they pass over the lateral regions of the bladder, ascend along the internal surface of the anterior abdominal covering of the fœtus, approaching each other as they get nearer to the navel, through which they emerge in order to enter the sheath of the cord, winding round the vein in their way to the placenta. (77) The vein on the contrary which proceeds from the placenta is of a larger calibre than that of the two arteries taken together. It is soft and extensible—and after having slightly meandered within the umbilical sheath penetrates through the navel into the abdomen of the fœtus, directs its course towards the inferior surface of the liver, enters the antero-posterior fissure of that viscus, unites with the left branch of the hepatic and vena portarum, and reaches under the name of the venous duct, the inferior cava. It has no valves, except one at its intro-abdominal bifurcation. This vessel, throughout its course, becomes obliterated after birth.

76. The omphalo-mesenteric vessels consist of a vein and an artery, the ramifications of which, externally to the fœtus, are seen distinctly on the umbilical vesicle (vesicula intestinalis). They accompany the cord as far as the navel through which they pass into the abdomen. They then separate, the former proceeding on the right to join the trunk or one of the branches of the mesenteric vein, and the latter on the left to join the superior mesenteric artery. These vessels are obliterated, as the vesicula umbilicalis to which they belong disappear, and lastly disappear in their turn. They have, however, been observed sometimes in the cord of the full grown fœtus, like whitish solid filaments. (Chaussier, Beclard.) In the recent case of an individual twenty years of age, who died of consumption, these vessels were found as pervious as when existing in the embryonic state, and contained blood. (Spakenberg.)[16]

77. When the Ovum is advanced to the second or third month of its fecundated existence (for the period varies in different examples I have had under my observation); its attachment to the Uterus, is firm and complete. Many of the vessels of the external surface of the chorion, which by this time have increased in size, while their free ends have luxuriantly branched out in innumerable minute vessels, have clustered together and formed what are in reality cotyledons—by means of which the said attachment is principally effected. (Personal observations and experiments.) The congeries of these clusters of vessels constitute the principal part of what has been called the Placenta, which grows in size and expands as the gravid uterus expands progressively during gestation.

78. The Cotyledons sometimes consist of only one short and very thick principal trunk—dividing itself, at a short distance from the surface whence it springs, into two, three, sometimes more, lesser trunks, and then again subdividing into thousands of smaller tubes;—at other times the cotyledons consist of two or three distinct straight trunks of different calibre springing from the chorion close to each other (as insulated clusters of lofty and straight trees are often seen here and there on a plain); in which case, the corresponding subdivisions being more numerous, the cotyledon is necessarily larger. (Personal observations, 1825, 1826.)

79. The main trunks of these cotyledons are ramifications of the umbilical vein and arteries, seen to spring from the subdivision of those vessels which are observed to run horizontally on the fœtal surface of the placenta, and which are the termination of the umbilical cord. Between these cotyledons there are spaces of various sizes in which the surface of the Chorion is clear of all filaments, vessels, or any other attachment or projection whatever,—such surfaces are smooth and shining. (Personal experiments, 1825, 1826.)[17]

80. The trunks of the cotyledons and their subdivisions whether springing from the vein or from the arteries of the cord have their coats made of the Chorion and amnion which accompany each cluster so as to form the thinnest pellicular receptacle for their ramifications. It follows hence, that when a coloured liquid, or even air is injected through the arteries of the cord, no escape of the injection takes place, nor can take place, from the terminal vessels of the clusters or cotyledons—and as it is found also that the same injection, if projected long enough (without lacerating any part of the gossamer-like structure we act upon) is brought back by the vein of the cord (which has no valves to prevent such a return) another conclusion is inevitable, namely that the terminal arterial vessels become, by a continuous arrangement, incipient radicles of the venous tubes. (Personal experiments, 1825, 1826.)

81. Now in as much as in the human placenta, expelled at the full period of gestation, before any experiment be undertaken to disturb its integrity, the lobes which it presents have each the appearance of a continuous mass, without any intervening spaces (79); and as these appear only clear, smooth, and shining, after maceration and much patient dissection that leaves nothing rough, or lacerated or divided by violence, behind; it follows that a something must have been removed, during the process of maceration and dissection, which before the employment of those processes occupied the spaces in question. (79.)

82. That something consists in a congeries of blood-vessels, arterial as well as venous, proceeding from the longitudinal vessels of the decidua covering the placenta (Dr. Hunter, Chaussier, Meckel, Lesauvages, myself). These vessels ramify in a manner analogous to that in which those of the fœtus have been described to ramify, (78, 79.) They penetrate between the interstices left by the minutest branches of the umbilical cotyledons. Their direction is lateral, perpendicular, oblique, and variously tortuous, in reference to the plane of the decidua whence they originate. Wherever they form a thick cluster, they are found to occupy one of the spaces already described (79). To facilitate this arrangement, and to render the distribution of the decidual vessels throughout the masses of the umbilical cotyledons more effectual—the membrane itself (decidua) is found to dip among the latter, dividing the general mass into lobes of various sizes, by which contrivance the decidua acquires an additional extension. (Personal Observations and Experiments.)

83. The decidual vessels are formed by continuous arterio-venous tubes. They reach, but do not connect themselves with the chorion. In the same manner as the terminal vessels of the umbilical cotyledons reach, but do not connect themselves with the superimposed decidua. When an attempt is made to remove (peel off) the latter from the surface of the placental mass, we notice certain attachments between them which are torn in the removal. These are the decidual vessels (82) and not as stated incorrectly by some, the terminal vessels of the umbilical system. (Recent German, and French, and Personal Experiments.) In the same manner as the umbilical vessels are accompanied by the chorion, the decidual vessels are accompanied by a membrane peculiar to the placenta, which I have called the _membrana propria_.

84. If we take a placenta which has been expelled from the womb, in all its integrity, between the fifth and seventh month, when the vascularity of the decidua is considerable, and after carefully washing its surface in tepid water, we plunge it in a weak solution of alcohol, so as to harden the decidua in some degree, we shall be able to slice off the latter from the surface of the placenta, at the depth of about the tenth of an inch, without injuring the delicate texture of the membrane. This should then be carefully macerated by turning the under surface upwards, under water, when, after a time, much of the tomentous attachment seen floating, will gradually be detached, and leave part of a smooth surface behind. If the membrane be then viewed with a strong magnifying glass, on its upper surface several orifices, with regular edges, but of various aperture, will be observed, through which, if we introduce a slender pipe and blow air into them, not only the longitudinal vessels in the decidua will be seen to fill with that fluid; but the short fragments of their ramifications pendent from the under surface of the membrane, will be distended, and the air will pass through them bubbling up through the water, thus denouncing their own vascular nature and arrangement. This is _an experimentum crucis_. (Original, 1826–27).

85. The orifices in the decidua have been denied by one or two recent writers, particularly by Professor Lauth; but they are admitted by all the rest of the modern physiologists and anatomists, from Dr. Hunter down to the latest experimentalist on the subject. It is through these that the injection, thrown into the uterine vessels, while the placenta is still adhering to the uterus, passes into that part of the placental mass which is formed by the decidual ramifications. In a very beautiful and most accurately conducted experiment made at the Middlesex hospital, by Dr. H. Ley, (March, 1833,) the particulars of which, I hope, to see published by that able physician; a red injection was pushed, without any difficulty,—laceration,—or extravasation, towards the adherent placenta, from the uterine vessels of a pregnant woman, who died of a disease of the heart, undelivered; when it was found to have penetrated, in the most regular and uniform manner, to the very remotest terminal ramifications of the decidual vessels. The placenta was then carefully detached, the decidual surface was carefully examined with magnifying glasses, no laceration could be detected, except what had been made by accident or violence in a small part of its circumference while the placenta was being detached from the womb. Orifices, as distinct and as properly organized as orifices can be in membranous textures, were seen in many parts of it by more than one competent and unbiassed person; and air was blown through some of them, or a small silver pipe introduced, without effort or laceration. Not the slightest vestige of extravasation, or lump of injection, was observed in any part of the intact placenta when cut into. This same result has been obtained, it is understood, in a recent injection by Sir A. Cooper, but the nature of the experiment is not yet known. The same result was obtained by Dr. Hunter, whose positive affirmation has been so recently questioned. The same result has been obtained by Lobstein. The same result has been obtained by Chaussier. Such a result is believed to be correct by Magendie. Professor Mende, in a report to the Obstetrical Society of Gottingen, states having made the experiment of injecting the uterine vessels with air—and with milk, in the case of a woman who died (1830) after the Cæsarean operation, the placenta remaining firmly adherent to the uterus, and he obtained the like result—as Hunter and others. Can we, therefore, refuse credence to such a host of eminent men and experimenters?