At the end of the fourth month the produce of conception is no longer called the embryo, but the foetus. The body is from six to eight inches in length, and weights seven or eight ounces. The sutures and fontanelles are now very large; and little white hairs may be seen scattered over the scalp. The development of the face is still imperfect. The eyes are now closed by their lids; the nostrils are well formed, and the mouth is shut in by the lips. The tongue may be observed far back in the buccal cavity; and the lower angle of the face is rounded off by what a little later will be a well-formed chin. The umbilical cord is attached to the abdomen still higher up, though as yet much below the centre of the body. A foetus, born at this time, may survive for several hours. I once made desperate efforts to save one born at this age, in order to satisfy the anxious parents, and to cause it, if possible, to grow up; it was born at three P.M.; but in the middle of the night the disappointed father called me up to announce that the child had ceased breathing, and to ask what should be done in that case!
At five months the body of the foetus is from eight to ten inches long, and weighs from eight to eleven ounces. The skin has now a fairer appearance, and is more consistent; the eyes can on longer be distinguished through the lids, owing to the increasing thickness of the latter.
At six months the foetus is from eleven to twelve and a half inches in length, and weighs about sixteen ounces, more or less. The hair upon the scalp is thicker and longer, the eyes remain closed; and very delicate hairs may be seen upon the margins of the eyelids and upon the eyebrows. The nails are solid; the scrotum small and empty; the surface of the skin appears wrinkled, but the dermis may be distinguished from the epidermis.
At seven months the length of the foetus is from twelve and a half to fourteen inches; its weight is about fifty-five ounces; and it is both well defined and well proportioned in all its parts. The bones of the cranium, hitherto quite flat, now appear a little arched; and as the process of ossification goes on the arching increases till the vault is quite complete.
At the eighth month the foetus seems to thicken up, rather than to increase in length, since it is only from sixteen to eighteen inches in length, while its weight increased to four or five pounds. The skin is red, and characterized at this period by a fine downy covering, over which is spread a quantity of thick viscous matter, called the sebaceous coat. The lower jaw has now becomes as long as the upper one; and in the male the left testicle may be found in the scrotum.
At nine months the anxious time has arrived; the foetus is from nineteen to twenty-three inches in length; and weighs from six to eight pounds, on an average. Some children weigh very much less; some as much as fourteen pounds; but such extremes are very rare. In most instances the child is covered with a whitish, sebaceous matter, called casseusa, which is really a secretion from the child’s skin, which may be dissolved and removed from the surface after birth by rubbing with some unctuous material, such as oil or lard.
Upon a careful review of the preceding account of the growth and development of the foetus, it will be seen that this growth is much more rapid in the first and in the last three months of its intra-uterine life, than during the middle of this period.
DESCRIPTION OF FOETUS AT FULL TERM.- It must be evident that all the mechanical difficulties attending child-birth increase with the development of the child; hence the necessity of particularly studying the most voluminous portion, in order that we may intelligently adapt it to the passage in the pelvis through which it must pass. The most voluminous, the least yielding and compressible, and by far the most difficult part to manage in parturition is the head; and of course where this may pass, the remainder of the body can follow with comparative ease.
The shape of the foetal head is ovoidal; the posterior layer being larger than the anterior. The cranium, with which as accoucheurs we are principally interested, is composed of the os frontis, the occipital, the two parietal and the two temporal bones. These are articulated by means of sutures, which in the foetus at full term are usually cartilaginous. Angular spaces, composed also cartilage, and called fontanelles, are left at the crossing of these sutures. Each suture and fontanelles has its particular designation.
The sagittal suture, arises from the root of the nose, dividing the frontal bone on the mesian line, runs across the top of the head to the occipital bone, and sometimes divides that bones to its very base.
The coronal suture crosses the sagittal at right angles, uniting the os frontis to the parietal and temporal bones.
The lambdoidal suture also crosses the sagittal, although at a more acute angle, uniting the occipital bone to the parietal a nd temporal bones. Where it crosses the coronal suture there is left a large, quadrangular, cartilaginous space called the anterior fontanelle. The crossing of the lambdoidal suture with the sagittal, leaves a three-sided space, smaller than that of the anterior fontanelle, and called the posterior fontanelle. There are other sutures and fontanelles, formed in a similar manner, between all the bones which compose the foetal head; but these are the only ones of practical importance to the accoucheur. By means of these sutures and fontanelles the head may be compressed so as to require less space during parturition, thus rendering this function less frequently injurious to both mother and child than must otherwise be the case.
The diameters of the foetal head at term may be reduced, for all practical purposes, to seven in number. The occipito-mental, (a b, Fig. 61,) extending from the posterior fontanelle to the chin, is five and one-fourth inches. The occipito-frontal, d e, extends from the
occipital protuberance to the frontal boss, is four and one- fourth inches. The sub-occipito bregmatic, c f, extends from the central point between the foramen magnum and the occipital protuberance to the anterior fontanelle, and measures three inches three-fourths. These are called antero-posterior diameters. The transverse diameters are, one bi-parietal, a b, (Fig. 62,) extending from one frontal protuberance to the other, three inches and three-fourths; the other, the bi-temporal, c d, (Fig. 62,) extending from the zygomatic process of the side to the same point on the other, measures three inches. Finally, there are also two vertical diameters: First, the vertical diameter, i g, (Fig. 61,) extending perpendicularly from the highest point of the vertex to the anterior boundary of the foramen magnum, measures three inches and three-fourths. Second, the fronto-mental, d a, (Fig.61,) form the frontal boss to the lowest point of the chin, measures three inches.
Now, it will be readily seen, that the antero-posterior diameter is quite too long to pass any diameter in the well-formed pelvis, even in the dried state, where the largest diameter is only five inches. Hence it must be apparent that, in order for the head to be capable of passing in parturition, the longest diameter must lead the way; that is, the long diameter of the head must be made parallel to the axis of the pelvis by making either the occiput or the chin lead the way. When this is accomplished it is evident that all the other diameters of the head will be permitted to pass though a well-formed female pelvis. And the more perfectly the antero-posterior diameters of the head can be made parallel with the general axis of the pelvis, the easier. other things being equal, will the child be born.
A great difference exists between the heads of male and female children, in the greater size and more complete ossification which are found to obtain in the former. As a proof of this, we may adduce the one observed fact, that the proportion of still- born boys to still-born girls, is one hundred and fifty-one of the former to one hundred of the latter. And even of those born alive, a much larger number of boys than of girls die in infancy from injury received during birth. And finally, of the mothers who succumb to consequences of child-birth, a majority have given birth to boys. Thus it appears that the growth of the male portion of the race costs much more suffering, and a greater loss of life, than does that of the female portion.
One more fact needs to be studied in this connection; and this the articulation of the child’s head to its trunk. The occiput is articulated with the atlas in such a manner as to admit of great flexion and extension, while at the same time the atlas is to placed upon the axis as to admit of great rotation, much more freedom of movement in either articulation than in possible in the adult. Hence it makes little difference, so far as the child’s neck is concerned, whether the occiput or the chin lead the way in parturition. It is, however, much better, as is usually the case, for the occiput to lead the way; for, as the chin thus rests upon the sternum of the foetus, the long diameter of the head corresponds more exactly with the long diameter of the body of the foetus, and consequently the whole long diameter is more in harmony with the axis of the cavity of the pelvis. Thus the direct force of each contraction of the uterus is received by the propelled body in a mass, none of the force being lost, as would necessarily be the case if the chin were to lead the way. For here every contraction would tend to throw the occiput back upon the spine, in which, instead of finding a firm base an in the natural position of the chin upon the sternum, the tendency would be to break the child’s neck at each contraction.
