At the time of a fruitful connection, which can only occur, it must be remembered, when the ovum is ripe, the male principle is carried into the Womb, (B, Plates I. and III.) and is then supposed, by some, to meet with the ovum which has descended down the Fallopian Tube (f, Plates I. and III.) from the Ovary, so that the union of the two takes place, according to this view, either in the Fallopian Tube or in the Womb. Others, however, suppose that the ovum does not leave the Ovary before conception, but that the male principle passes down the Fallopian Tube and meets it there, and that it is several days after before it reaches the Womb. There are many facts and arguments brought forward in support of each view, all of which will be set forth in my forthcoming work on the reproductive functions. All that is known for certain is, that the two principles must unite in one place or the other, and that the ovum must pass down the Tube into the Womb, either before impregnation, or after.
The union of the two principles in the Womb appears so likely an event that it is scarcely possible to avoid thinking that it really does then take place, but at the same time there are very strong reasons for adopting the opinion that it takes place in the Ovary. Among others may be mentioned the phenomenon of extra uterine conception, which will be more fully alluded to in another place. In these cases the fœtus is found outside of the Womb, in the Tube, or the Ovary, or even in the Abdomen, among the intestines. Such an occurrence seems to render it almost certain that the ovum must have been fecundated in the Ovary, because we cannot well conceive, if it were not so, how it could reach the outside of the Womb. This difficulty is not, however, regarded as insuperable, by the advocates of the opposite theory. Possibly conception may occur in both ways.
There are many causes which prevent conception, or, in other words, which produce barrenness and sterility. These various causes cannot be all explained, except in connection with a full explanation of the process of reproduction, and of the nature of many female diseases. In my work on "The Diseases of Woman," I have given a chapter on this subject, and have also referred to the present work as one in which it would be more fully treated. This reference, however, was made in mistake; the subject is not needed here, but will be in the other work, on the reproductive functions in which it will be discussed at length.
CHAPTER IV.
FŒTAL DEVELOPMENT.
The last Chapter brought us up to the point of conception, or the first commencement of the new being. The next step is to exhibit its various stages of development, and to show how it is nourished and maintained in its proper position. This is requisite in order to understand the origin of many diseases and accidents which occur during gestation, and also to explain the various signs by which it is determined whether a female is pregnant or not.
FŒTAL DEVELOPMENT.
The development of a perfectly formed human being from the egg in which it originates, is one of the most astonishing phenomena that can come under our observation, and is eminently deserving the study of every rational being. The present explanation of it must necessarily be brief, being merely intended to make the main subject more clear.
It has already been remarked that it is uncertain whether the ovum is impregnated before it is brought into the Uterus, or after it arrives there; but be that as it may, nothing has yet been discovered in the Womb till several days after conception. Some physiologists tell us that the rudiment of the new being may be found there about the sixth day; but others again assure us that it cannot be found before the twelfth, at which period our explanation of its development will commence.
At the twelfth day the ovum is about the size of a large pea, it is composed of a vesicle containing a thick fluid, called the germ, which corresponds to the opaque substance seen in the white of a fecundated bird's egg, and of a yellowish substance, in which it floats, called the vitellus, which answers to the yelk. The whole being surrounded by two membranous coverings, the outer one called the chorion, and the inner one the amnion. Between these is a gelatinous substance, and within the amnion is a fluid, called the liquor amnii. The two membranes, the liquor amnii, and the inclosed ovum, are called the ovulum! Immediately after conception the uterus begins to secrete, from its inner walls, another membrane, very delicate, called the decidua. This lines the whole cavity, so that when the ovulum passes out of the tube it is met by this lining which seems to prevent its entrance into the womb. The ovulum, however, presses upon it and so makes a depression, like a nest, in which it lies. This prevents its moving about, or falling to the bottom of the womb.
The weight of the entire ovulum is about one grain. The embryo commences in the germ, and may now be seen about the size of a pin's point. The vitellus removes away from it, but remains connected by a small pedicel or thread-like tube, down which it is gradually absorbed as nutriment. A small white thread, scarcely perceptible, may be seen sometimes as early as this period, being the commencement of the brain and spinal marrow. The mouth is visible also from the twelfth to the twentieth day, and frequently the eyes. These are placed at first on the side of the head, like those of quadrupeds, and move round to the front afterwards.
At twenty-five days, the embryo is about the size of a large ant, which it also resembles in form. It begins to have a little more consistence, and the future bones begin to resemble cartilage, or gristle. A small groove may be seen denoting the neck, which thus indicates the separation of the head from the trunk. The weight is three or four grains.
The first month, it is about the size of a Bee, and is somewhat like a small worm bent together. The arms may be seen like two little warts. They are first formed under the skin, and shoot out like buds, growing straight from the body; afterwards they become folded together, in a curious manner, upon the breast. The head is as large as the rest of the body, and upon it we can now see distinctly the eyes, like two black dots, the mouth, like a line, and also the nose. The lower extremity is lengthened out like a tail. Weight about ten grains.
The second month. Every part has now become much more developed, and the general form is that of a human being. The superior members are much more elongated, and the inferior ones begin to be distinguished, forming in the same manner as the others. The fingers are united together by a membrane, like the web on a Frog's foot. In the ribs, clavicles, and jaw bones, a few points can be seen ossified, the cartilage beginning; to harden into bone. The rudiments of the first teeth are also visible. The weight is about one drachm, and the length one inch.
At about seventy days the eyelids are visible, the nose becomes prominent, the mouth enlarges, and the external ear may be seen. The neck is well defined. The brain is soft and pulpy, and the heart is perfectly developed.
Every organ is originally formed without either blood or blood vessels. The circulation which afterwards takes place in them is merely for their subsequent development. The heart is perfect in all its parts, and even has a slight motion, before the blood is found in it.
Three months. All the essential parts are well defined. The eyelids distinct, but firmly closed. The lips perfect, but drawn tightly together. The heart beats forcibly, and in the larger vessels red blood is seen. The fingers and toes are defined, and the muscles begin to be apparent. The organs of generation are remarkably prominent, but still it is somewhat difficult, at first, to distinguish the sex by these organs, notwithstanding their development, as the principal parts in both are nearly identical in form. It can, however, be ascertained by other circumstances, as the form of the head, dorsal spine, thorax, and abdomen. It now weighs about two ounces and a half, and measures four or five inches in length.
Four months. The development is remarkably increased. The brain and spinal marrow becomes firmer, the muscles distinct, and a little cellular tissue is formed. The abdomen is fully covered in and the intestines are no longer visible. A little of the substance called meconium even collects in the intestines, the same as is found in at birth. It now weighs seven or eight ounces, and measures six or seven inches. The bones are ossified in a great part of their extent, and the rudiments of the second set of teeth are visible, under the first.