Of Con- in different climates. In Europe it takes place comception. monly between the fourteenth and sixteenth year. This important era is marked by certain changes both in the mind and body. The girl feels sensations to which she had been formerly unaccustomed. She loses a relish for her former amusements, and even for her youthful companions. She seeks solitude, indulges in the depressing passions, and these are excited by the most apparently trifling causes. She feels occasionally certain desires which modesty represses; and it is by degrees only that she regains her former tranquillity.

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The changes in her body are even more strongly marked than those in her mind. Her breasts assume that form which adds to the beauty of her person, and renders them fit for nourishing her infant; and every part of the genital system is enlarged. A periodical discharge from the uterus renders the woman perfect.

In young men the same causes produce very different effects. The lad, about fifteen or sixteen, feels a great increase of strength; his features expand, his voice becomes rough, his step firm, his body athletic; and he engages voluntarily in exercises which require an exertion of strength and activity. The changes in his mind are as strongly marked as those in his body. He loses that restless puerility which had distinguished his early years, and becomes capable of attending steadily to one object. His behaviour to the fair sex is suddenly altered. He no longer shows that contempt for women, which he had formerly betrayed. He is softened, approaches them with deference, and experiences a degree of pleasure in their company, for which he can scarcely account. In him too there is an important change in the condition of the genital organs.

2. Unless the parts which constitute peculiarity of sex be in a healthy, vigorous, and natural state, conception cannot take place.

In women, conception is prevented if the organs be too much relaxed; if there be obstruction between the external and internal parts; if any preternatural discharge take place from the internal parts; if the menstrual evacuation be not natural in every respect, and if the appendages of the uterus, called fallopian tubes, and ovaria, be not of the natural structure.

In men, the same circumstance happens if the organs be too much relaxed; if the orifice of the urethra be in an improper situation; if the urethra be diseased; if the testes be not in a natural healthy state; and if there be any defect in the erectores penis, which prevents the proper erection of that organ.

3. The sexual intercourse cannot be successful unless somewhat necessary for conception be furnished by both

sexes.

This consists in the male of a fluid secreted by the testes; and in the female, of a detachment of a substance, supposed to resemble a very minute vesicle situated in the ovarium, and called by physiologists

ovum.

Each ovarium contains a number of these vesicles. After every conception, certain marks of the detachment of the ovum remain in the respective

ovarium.

When the circumstances required for conception concur, a being is produced which generally resembles both parents. This resemblance is most strikingly marked in the human subject, when one of the parents

is an European, and the other an African. What is of Concalled a mulatto is produced. ception.

The human race possesses the power of propagation in common with all the other species of the animal kingdom, and also, it has been said, with the vegetable kingdom.

As generation then, as it has been styled, is common to two of the kingdoms of nature, it has been imagined by ingenious men, that this wonderful operation is regulated in both by a certain general law. But they have differed much in their account of this law. The question at issue between the two parties is whether the embryos of animals be prepared by the sexual intercourse out of inorganic materials, or whether they pre-exist in the bodies of animals, and are only developed as it were by that intercourse. The former of these opinions is called the doctrine of epigenesis, the latter that of evolution.

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Both doctrines have been maintained with much ingenuity by equally respectable authorities. Negative arguments have been adduced in favour of the one, positive in support of the other, and it must be confessed that the balance between them seems nearly equal. The pre-existence of ova in the oviparous animals appears a positive argument in favour of evolution; but the satirical remark of a late witty author, * that, were * Blumenthis theory true, every individual of the human race bach. must have been lodged in the ovaria of our first parent, by affording a negative argument in favour of epigenesis, restores the balance.

The various arguments advanced on each side by the opposite parties in this dispute are so very numerous, that we cannot attempt to detail them in this work; and on a subject which has divided the opinions of so many able physiologists, it would be presumption to decide peremptorily.

If generation be regarded as an animal operation, one is led to inquire whether the product be the result of the combined influence of both sexes, or whether it be produced by either sex alone.

The first opinion was generally adopted by physiologists, till about the end of the 17th century, when an accidental discovery convinced many that the embryo was produced by the male parent alone; and another discovery some years afterwards again overturned that opinion, and rendered it believed by not a few that the embryo is furnished exclusively by the female parent.

Several circumstances concurred to render the first opinion probable; the structure of the organs which constitute peculiarity of sex in both parents, the circumstances necessary for successful impregnation, and the similitude of children to both parents, appear very strong arguments in its favour.

The second theory, although first brought into vogue about the end of the 17th century by the discoveries of Leeuwenhoeck, had been formerly proposed by the followers of Pythagoras. Their argument was analogy: the seed, said they, is sown in the earth, nourished and evolved there; so the male semen is sown in the uterus, and in the same manner nourished and evolved.

Leeuwenhoeck's discovery seemed a more conclusive argument in favour of the theory than vague analogy.

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Of Con- He observed innumerable animalcula in the seminal ception fluid of the males of many animals. These he imagined to be embryos.

But as animalcula of apparently the same nature have been observed in many animal fluids besides the semen masculinum, the opinion of Leeuwenhoeck and the theory itself are overturned.

It was owing principally to the labours, industry, and ingenuity of Baron Haller, that the third theory, that of the pre-existing germ, became fashionable.

His observations seem to contain a demonstration of the fact.

Those who have adopted this theory, imagine that the semen masculinum possesses the power of stimulating the various parts of the pre-existing embryo. And hence they attribute the similitude to both parents, and particularly the appearance of the hybrid productions, to that fluid nourishing certain parts, and new-arranging others. But if this were true, then the semen masculinum of all animals should possess the power of stimulating the germs of all female animals; and besides, in each class of animals it should possess certain specific powers of giving a direction to the growth of parts. Experience, however, has not proved this to be the case, for the hybrid productions are very limited; and we may be permitted perhaps, without the imputation of arrogance in pretending to search into the intentions of the Author of nature, to observe, that had the semen masculinum been possessed of such powers, the whole species of animals would have been soon confounded, and the whole animal kingdom would soon have returned to that chaos from which it has been allegorically said it originated.

Yet we are reduced to the alternative of either rejecting the theory, or of believing that the semen does possess the powers alluded to. If we examine attentively the anatomical discovery on which this theory is built, we shall perhaps be inclined to believe that the foundation of the whole is very insufficient; and hence to conclude that the great superstructure is in a very tottering condition. If it be possible that the attachment of the chick to the yolk of the egg should be in consequence of inosculation, the theory must fall to the ground. Haller has endeavoured to obviate this objection, but not with his usual judgment.

Two circumstances, however, seem to show that the attachment is really by inosculation: 1. That vessels are seen in the membrane of the yolk evidently containing blood before the heart of the chick begins to beat; yet these vessels afterwards appear to depend on the vascular system of the chick. And, 2. That in many animals, as in the human subject, the umbilical cord seems to be attached to the abdomen by inosculation; for there is a circle round the root of the cord which resembles a cicatrix, and within a few days af ter birth, the cord uniformly drops off at that very circle, whatever portion may have been retained after delivery.

There is one objection equally applicable to all the three theories, viz. the difficulty of explaining the steps of the process. A variety of explanations have been offered by ingenious men. Spallanzani and Mr John Hunter lately, Haller and Bonnet formerly, have rendered themselves conspicuous on this subject. Spallanzani, in particular, appears to many to have produced,

by his artificial impregnation, the most convincing Effects of proofs of the pre-existence of the germ. But to what Impregnado his celebrated experiments amount? They show, that tion. in all animals it is necessary that the semen masculinum should be applied to the somewhat expelled by the female during the coitus, otherwise impregnation cannot take place. But was not this universally acknowledged before the abbé was born? In the unfortunate frogs who were the subjects of his experiments, the whole operation of generation was completed except the application of the male seuien to the substances expelled by the female. Nature, by establishing that the business should be carried on in water, shows that the semen must be diluted, otherwise it cannot fecundate.

The abbé only imitated nature. He left the question in the state in which he found it. His experiment on the bitch may appear more conclusive'; but alas! it has never succeeded with any person but himself.

On the whole, since the process of generation is so obscure that no rational explanation of it has yet been offered, are we not entitled to conclude that the general theory which accounts most satisfactorily for the various phenomena which impregnation exhibits is the best; and consequently, that the product of genera tion cannot pre-exist in the body of either parent exclusively?

CHAP. II. Effects of Impregnation.

IN consequence of impregnation, certain important changes take place in the uterine system of the human subject. We shall consider the natural changes only. On some occasions, there are morbid changes; but we shall not notice them, except in so far as some of them serve to illustrate the nature of the usual ones.

The first visible change is on the ovarium. One of those organs swells out at one point like a small papilla, then bursts, and somewhat is discharged.

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A substance is found in the ovarium after this, which is called corpus luteum. Roederer has described very accurately its appearance a few hours after delivery. He says "corpus luteum locatur in rotundo apice. Totam ovarii crassitiem occupat, immediatè 'pone ovarii membranam illa sede tenuiorem locatum; ab ovario cum quo cellulosæ ope cohæret separari sine læsione potest; nulli peculiari ovarii rima respondet: neque canalis in illo excavatus, sed totum solidum est. Luteus color est, substantia acinosa, acinis admodum compactis et ad sese pressis ambitus rotundus. Potest aliquo modo, velut in glandulis suprarenalibus, duplex substantia distingui, corticalis et medullaris; quarum illa inæquais crassitiei 1-2 lin. lutea comprehendit hanc medullarem albam, quæ tenuis et membrana quasi callosa, alium nucleum flavum includit cassiorem *." It is very large soon after conception, and then gradually be- Icones, comes smaller; but never totally disappears. Roederer, mani obobserves, " post puerperium eo magis contrahi et indu-servat. ilrari illa corpora videntur, quo remotior fit partus ; lust. p. 42. qualia videlicet observantur in feminis quæ nuper partum non ediderunt.

"Lutea corpora quo serius à partu observantur cuncta glandulis suprarenalibus similia esse videntur, duplice nempe substantia, exteriore corticali, solida seu flava lutea et nucleo fusco: velut etiam ille glandulæ compressa sunt +." In cases where there is a plurality of

children,

*Roederer

Uteri Hu

P. 30.

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The next change in the human uterine system which deserves notice is that in the fallopian tubes. They swell out towards the fimbriated extremity, and form a cavity which has been called antrum. Ræderer was the first who observed and accurately delineated this change.

He says, p. 14. loco citato, "In hoc etiam utero antrum tubæ dextræ apparet, c. f. tab. i. not. 5. ubi quidem in utraque tuba adest, in hujus iconis utero ad solam tubam dextram antrum pertinet. Ad uterum feminæ octiduum puerperæ non longe a fimbria in istiusmodi antrum tuba sinistra prominet: dextra quidem sine antro est, sed versus fimbriam ita flectitur ut ultima flexura dimidium pollicem ultra reliquam tubam efferatur. Tubæ feminæ quæ mox a maturo partu mortua est, et alterius tres dies puerpera antris quidem carent, sed multum versus simbrias dilatantur. An est facta conceptione ista antra nascuntur?

"In uteri, tab. iv. ovario dextro luteum corpus latet in uteri feminæ octiduum puerperæ ovario sinistro; in -uteri, tab. i. ovario sinistro." He adds, " ulteriori indagine ista antra non indigna esse mihi videntur. Licebit forsan conjectare aliquid liquoris ex vesicula graafiana in tubam lapsum et ad introitum morans illam dilatam."

But the most astonishing changes are those produced in the uterus itself. Its parietes separate, a cavity is formed which becomes filled with a fluid, and the os uteri is closed up. The matter contained within the cavity soon assumes an organized form. It is said that some time after conception, a small vesicle is observed attached at one point to the internal surface of the uterus; that the rest of the parietes is covered with a gelatinous fluid; and that the whole internal surface assumes a flocculent appearance. By degrees the vesicle, which is in fact the ovum containing the embryo, increases so much in size that it nearly fills the whole cavity in which it is contained, and then its structure becomes the object of our senses.

The increase of size in the uterus is very gradual. It is at first confined almost entirely to the fundus, and it proceeds so slowly that it does not leave the cavity of the pelvis till nearly the fourth month. The principal change in the cervix for the first five months is the complete closure of the orifice, which is effected by a gelatinous fluid afterwards the cervix is gradually extended, and at last its form is obliterated, the whole : uterus becoming like an oval pouch.

After the fifth month the increase of size in the uterus is very rapid. The fundus can be just felt above the pubes about the fifth month, but at the end of the ninth month it extends to the scrobiculus cordis.

Some authors have alleged that the changes in the cervix and in the situation of the fundus are so uniformly regular in every case, that by attending to them it is possible to ascertain the exact period of impregnation. But in this respect they are much mistaken; the changes being not only different in different women, but also in the same woman in different pregnancies.

The texture of the parietes of the uterus seems much

altered after impregnation. It becomes spongy and Effects of fibrous. The fibres run in very different directions, and Impregnafrom their power and appearance are certainly muscular. The blood-vessels become much enlarged, but are still in a tortuous direction. They are particularly large at one part of the uterus.

The lymphatic vessels, which in the unimpregnated uterus cannot be demonstrated by anatomists, become, as well as the blood-vessels, remarkably large.

The ovum is not often expelled entire till after the eighth or twelfth week after conception. It is shaped somewhat like an egg, and is about the latter period about four inches in length. When cut into, it is found to consist of four layers or membranes, and to contain a foetus surrounded by a certain quantity of water, and connected to one part of the parietes (which is considerably thicker than the rest) by a vascular cord.

The external membrane covers the whole ovum. It is thick, spongy, and very vascular, the vessels evidently deriving their blood from the uterus; it has three perforations which correspond with the openings of the -os tincæ and fallopian tubes. It has been called deciduo, tunica filamentosa, &c. but its most ordinary appellation is spongy chorion.

The second membrane proceeds from the edges of that part into which the vascular rope which connects the foetus is attached. It was first pointed out to anatomists by Dr William Hunter, and called by him decidua reflexa. The name unfortunately records to posterity the absurd idea respecting its origin which was entertained by Dr Hunter. It is not so thick and spongy as the former membrane, nor so vascular. It lies loosely between the external membrane and that to be next described; but it appears only for a short time, as it soon becomes blended with the others.

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The third membrane is thin and transparent, but strong. It is lined with the fourth membrane, and lies in the same situation with it. It contains no vessels at this period of impregnation conveying red blood in the buman subject, but in the cow the vessels are very distinct at every period. This membrane however in the early period of impregnation is very vascular, and its vessels are derived from the foetus. The history of a case of morbid impregnation, where the foetus was extra-uterine, detailed by Dr Clarke in the "Transactions of a Society for the Improvement of Medical and Chirurgical Knowledge," proves this circumstance very clearly. He says, p. 220. a laceration was found to be in the fallopian tube about an inch and a half in length, each extremity of which was about an equal distance from the respective termination of the tube in the fimbria and in the uterus. The distension of the tube at this part was nearly of the size of a large walnut, forming a kind of pouch. More of the coagulated blood being removed from the lacerated part, the shaggy vessels of the chorion immediately appeared, interspersed with small coagula, and lying in contact with the internal surface of the pouch formed by the fallopian tube; these being separated, and the chorion divided, the amnios shewed itself, containing a fœtus perfectly formed of above six or seven weeks growth," &c. This membrane is called the true chorion.

tion.

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Effects of parent than the former. It lines the whole internal Impregna- surface of the ovum, and together with the chorion is

tion.

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continued along the vascular cord which connects the ovum and foetus. Between this membrane and the chorion, near the insertion of the vascular cord, a small white vesicle appears very distinct at this period; it was first described and delineated by Dr W. Hunter, and was called by him vesicula umbilicalis. At the full period of utero gestation it is no longer visible, being then quite transparent.

The foetus at this period is between two and three inches in length, and its external conformation is nearly complete.

The fluid contained in the ovum is in such quantity as to prevent the foetus from touching the parietes of the covering in which it is included. It is a clear watery fluid, of greater specific gravity than water, and of a saltish taste. When examined chemically it is found not coagulable by heat or alcohol, and to contain a proportion of ammoniacal and sea salt. This fluid is called liquor amnii.

The connection of the parts thus enumerated with the uterus cannot be explained, unless the appearance of the ovum at the full period of gestation be described.

The ovum then consists of three membranes; a spongy vascular substance called placenta, to which the fœtus is connected by a vascular rope, and the liquor amnii.

The three membranes consist of the spongy chorion, the true chorion, and the amnios.

The spongy chorion covers the whole. Its vessels are numerous, and they can be filled by throwing hot wax into the vessels of the uterus.

The true chorion and amnios are in the same situation as in the early months, being continued along the navel-string. They are quite transparent, and contain no visible vessels of any description.

The placenta is a large vascular spongy mass, of various forms in different cases, most generally approaching to a round one, placed on the outside of the true chorion, between it and the spongy chorion. Its external surface is lobulated; its internal or that towards the foetus is smooth, except from the rising of the blood-vessels.

It is not attached to the uterus at any regular place, being sometimes at the cervix or side, but most generally about the fundus. On the one side it receives blood from the mother, and on the other from the child. Mr John Hunter was the first who clearly traced the insertion of the blood vessels in the uterus into the placenta. He describes it thus (D): "The late indefatigable Dr M'Kenzie, about the month of May 1754, when assistant to Dr Smellie, having procured the body of a pregnant woman who had died undelivered at the full term, had injected both the veins and arteries with particular success; the veins being filled with yellow, the arteries with red.

"Having opened the abdomen, and exposed the uterus, he made an incision into the fore part, quite through its substance, and came to somewhat having the appearance of an irregular mass of injected matter, which afterwards proved to be the placenta. This ap

pearance being new, he stopped, and greatly obliged Effects of me by desiring my attendance to examine the parts, in Impregnawhich there appeared something so uncommon.

"I first raised, with great care, part of the uterus from the irregular mass above mentioned; in doing which, I observed regular pieces of wax, passing obliquely between it and the uterus, which broke off, leaving part upon this mass; and when they were attentively examined, towards the uterus, plainly appeared to be a continuation of the veins passing from it to this substance or placenta.

"I likewise perceived other vessels, about the size of a crow quill, passing in the same manner, although not so obliquely these also broke upon separating the placenta and uterus, leaving a small portion on the surface of the placenta; and, on examination, they were discovered to be continuations of the arteries of the uterus. My next step was to trace these vessels into the substance of what appeared placenta, which I first attempted in a vein; but that soon lost the regularity of a vessel, by terminating at once upon the surface of the placenta, in a very fine spongy substance, the interstices of which were filled with the yellow injected matter. This termination being new, I repeated the same kind of examination on other veins, which always led me to the same terminations, never entering the substance of the placenta in the form of a vessel. I next examined the arteries, and, tracing them in the same manner toward the placenta, found that they made a twist, or close spiral turn upon themselves, and then were lost on its surface. On a more attentive view, I perceived that they terminated in the same way as the veins; for posite to the mouth of the artery, the spongy substance of the placenta was readily observed, and was intermixed with the red injection.

op

"Upon cutting into the placenta, I discovered, in.. many places of its substance, yellow injection; in others red, and in many others these two colours mixed. This substance of the placenta, now filled with injection, had nothing of the vascular appearance, nor that of extravasation, but had a regularity in its form, which shewed it to be a natural cellular structure fitted for a reservoir for blood.

"In some of the vessels leading from the placenta to the uterus, I perceived that the red injection of the arteries (which had been first injected) had passed into them out of the substance of the placenta, mixing itself with the yellow injection. I also observed, that the spongy chorion, called the decidua by Dr Hunter, was very vascular, its vessels coming from, and returning to, the uterus, being filled with the different coloured injections.".

tion.

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Effects of child was separated. Yet, if a small portion of the Impregna- edge of the placenta be detached, such a quantity of tion. blood escapes from the uterine vessels of the mother, as sometimes proves fatal to life: a circumstance which clearly shews that the blood is still conveyed into the cellular part of the placenta.

It has been said, that the placenta on one side receives blood from the foetus. In fact, the greatest part of the placenta seems to be made up of ramifications of the foetal vessels. The internal iliacs of the foetus are conveyed, through the vascular rope which connects the placenta and child, into the placenta: they then ramify into as many minute branches as the pulmonary arteries do in the lungs of the adult; they then terminate in various branches, which, uniting, form one large trunk that is conveyed along the vascular rope, and returns all the blood which had been distributed by the arteries.

As Mr Hunter remarks," the arteries from the foetus pass out to a considerable length, under the name of the umbilical cord; and when they arrive at the placenta, ramify upon its surface, sending into its substance branches which pass through it, and divide into smaller and smaller, till at last they terminate in veins: these uniting, become larger and larger, and end in one which at last terminates in the proper circulation of the foetus. This course of vessels, and the blood's motion in them, is similar to the course of the vessels, and the *J. Hun- motion of the blood, in other parts of the body*." ter, loc. cit. P. 135.

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+ Harvey Exercit, de Partu

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The foetus, at the full period, weighs from between 6 and 7, to between 10 and 11 pounds, and measures from 18 to 22 inches. It is placed within the ovum in such a manner as to occupy the least possible space. This position has been beautifully described by Harvey. "Infans in utero utplurimum reperitur, adductis ad abdomen genibus, flexis retrorsum cruribus, pedibus decussatis, manibusque ad caput sublatis, quarum alteram 'circa tempora vel auriculas, alteram ad genam detinet, ubi maculæ albæ, tanquam confricationis vestigia, in cute cernuntur: spina in orbem flectitur, caput ad genua incurvato collo propendet. Tali membrorum situ qualem in sommo per quietem quærimus †.”

The fœtus is distinguished from the adult by a great many peculiarities in structure: these the limits of this work do not permit us to enumerate. We shall therefore notice only one peculiarity, which distinguishes the foetus not only from the adult, but even from the natus, viz. the distribution of the blood through its body.

It is well known, that, in the adult and in the natus, all the blood of the body, brought by the two cavæ into the anterior auricle of the heart, and from that into the corresponding ventricle, is distributed by the pulmonary artery over the whole substance of the lungs, by means of the most minnte ramifications; from whence it is returned by the pulmonary veins into the posterior auricle, and being then sent into the posterior ventricle, is, by its action, transmitted to every part of the body, through the aorta and its ramifications.

But in the foetus the blood follows another course. All the blood of the fœtus is returned from the placenta by the umbilical vein, which, penetrating the abdomen, passes between the lobes of the liver, and thence at right angles divides into two branches nearly, by one

of which, called ductus venosus, a considerable quantity Effects of of blood is carried into the vena cava; by the other the Impregna remainder of the blood is sent to the vena portarum ; tion. and, after having circulated through the liver, it too is brought by two short venous trunks, the vena cava hepatica, just above the diaphragm, into the vena cava. All the blood thus received into the vena cava, is carried to the anterior auricle; but a part only is transmitted to the corresponding ventricle, for by a particular apparatus, a quantity is at once sent into the posterior or left auricle. Anatomists have differed in opinion concerning the apparatus by which this is accomplished. As there is a small oval hole of communication between the auricles of the foetus, called foramen ovale, having a valve placed in such a manner as to prevent any fluid from passing from the left into the right, but to admit it from the right into the left, it has been generally imagined that the blood passed through that opening. But the simultaneous action of the auricles in the natus seemed to contradict this opinion. A discovery made by Dr Wolfe of Petersburgh appears to solve the riddle. He observed, that in the calf, before birth, the vena cava, at its entry into the heart, divides into two branches, by the one of which it sends blood to the right, and by the other to the left auricle. It is probable that a similar effect is produced in the human foetus by a different structure.

Of the blood sent by the right ventricle into the pulmonary artery, a small quantity only is carried to the lungs; for near the point at which that artery is divided into the two branches that go into the lobes of the lungs, a large branch is sent off, which joining the aorta and pulmonary artery, carries a great proportion of the blood immediately into it. What is circulated throngh the lungs is conveyed by the pulmonary veins into the left auricle, &c.

All the blood thus received into the aorta is distributed through the several parts of the system, and a large part of it is sent out by the internal iliacs, which, passing out at the abdomen, constitute the umbilical arteries, and distribute the blood in the manner already mentioned over the placenta, from which it is returned by the veins. The great difference then between the foetus and natus in the circulation of the blood, consists in the quantity distributed through the lungs.

To complete the description of the ovum at the full period of gestation, it only remains that we should say something on the vascular rope, which connects the placenta and foetus, and on the liquor amnii.

It termi

This rope is called the funis umbilicalis. nates by one end at the placenta,.and by the other at the centre of the abdomen of the fœtus. Its length and thickness differ materially in different cases. It is longer in the human subject than in any other animal. It is found generally to be from eighteen to twenty-six inches in length, and in thickness about the size of the little finger. Externally it is formed of the chorion and amnios, together with cellular substance. Internally it is found to be composed of three blood-vessels, and a quantity of gelatinous matter. The vessels consist of two arteries and one vein: the vein being as large as both arteries united. These go in a spiral direction, and often form knots by their coils or twistings. A very small artery and vein are likewise perceived to

go

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