tended vagina quite into the peritoneal sac, an accident that would be almost sure to kill his unfortunate patient.

Besides the organs now enumerated, the pelvis contains the obturator muscles and the large levator ani muscles, which descend like converging rays of a fan from the antero-lateral walls of the pelvis below the brim, and are inserted so as to lift or raise the end of the rectum and even the perineum upwards, so that not the rectum and perineum only, but the whole of the pelvic contents are directly or indirectly held up and sustained by these muscular organs. The stronger and more muscular the levatores ani the deeper is the sulcus betwixt the nates, and, in general, the better sustained are the contents of the basin. In the young and vigorous the sulcus is very deep; in the aged and the feeble it descends lower and lower or opens out, so that in very old or exhausted people the perineum becomes actually protuberant or convex.

Within the recent pelvis are numerous blood vessels and nerves, supplying the contained organs, besides large bundles of nerves that come from the sacral foramina and soon leave the cavity, passing outwards through the ischiatic notches to form the great sciatic nerve.

Here also are contained the ureters; while, overhanging the brim, are seen the psoas muscles, which seem to lessen the transverse diameter of the upper strait. Let the Student be particular to note the place and appearance of the psoas muscles as they pass along the brim of the pelvis; and let him observe that, when a woman, who has recently been delivered, suffers from inflammation of the womb, she always experiences pain when she draws up the knees, because the overhanging bellies of the psoas muscles, in contracting to flex the thighs, press very painfully upon the inflamed globe of the uterus, which still juts up above the plane of the superior strait, filling up the whole of its transverse diameter.

vation; D and E are the external iliac artery and vein; F G the psoas muscles, H the rectum, I the womb, and K the bladder of urine.

I wish the Student to reflect that all the pelvic viscera are within, and not out of or beyond the pelvis; and I say so in this place to guard him against the very common mistake of supposing that any part of the womb-its fundus-is to be found jutting up above the plane of the superior strait. There are few drawings made to illustrate the inner genitalia in situ, that do not exhibit the fundus uteri on a level with or even higher than the plane of the strait. Kolrausch's most beautiful and admirable plate, the most perfect that has yet been produced, gives to all the internal organs their absolute right place. I assure the Student that whensoever he shall find that he can feel the fundus uteri by pressing his hand upon the hypogastrium and pushing the teguments downwards and backwards, he may make sure that he is touching a womb enlarged by pregnancy or by some disease.

CHAPTER II.

MECHANICAL INFLUENCE OF THE PELVIS.-OF THE MECHANISM OF LABOR AS DEPENDENT ON THE RELATIONS OF THE CHILD'S FORM TO THAT OF THE PELVIS.

VERY little seems to have been anciently known concerning what is now called the mechanism of labor as observable while the head or other parts of the child are passing along the canal of the pelvis. No one can doubt that Mauriceau and Lamotte, who were keen observers, must have often noticed the spiral movements of the advancing head or breech in cases of labor, for it is impossible that such circumstances should have wholly escaped their notice, or that of many other highly talented practitioners of our art. Nevertheless, it is very certain that they have nowhere given any clear account of the act of rotation, and I believe that it is now almost universally agreed that we are under obligations, for the first statement concerning it, to Sir Fielding Ould, of Dublin. That gentleman, in 1748, published "A Treatise of Midwifery, in three parts, by Fielding Ould, Man-Midwife." Lond. 8vo. pp. 203. Ould gives an account of the matter in his Preface, p. xvi., saying: "And to this end, I hope that the description of the head coming towards the world, with the chin turned to the shoulder, will be of very great advantage;” and he tells us of a case that occurred to him while he was in Paris, in which he seems to have obtained some obscure notions concerning rotation. His promulgation of the doctrine of rotation may be found, such as it is, at page 28: "When a child presents itself naturally, it comes with the head foremost, and (according to all authors that I have seen) with its face towards the sacrum of its mother, so that, when she lies on her back, it seems to creep into the world on its hands and feet. But here I must differ from this description in one point, which, at first sight, may probably seem trivial: the breast of the child does certainly lie on the sacrum of the mother, but the face does not; for it always (when naturally presented) is turned either to one side or the other, so as to have the chin directly on one of the shoulders."

In the next paragraph, which is on p. 29, Sir F. Ould explains his notions of the causes of the head's obliquity, and though he had no very exact perceptions of the facts, it is doubtless to him we should look as the pioneer in this particular section of our obstetrical labors. Since the date of Sir Fielding Ould's publication, the views of the profession upon the mechanism of labor, in so far as the volume and form of the pelvic canal and those of the foetal head are concerned, have become quite settled, and it is not difficult to set it in such a light as to make it easy of comprehension for the Student. To this end, I ought to say that the gravid womb at full term is about twelve inches in length from the os to the fundus, and from seven to eight inches across at the place of its greatest breadth. A child in utero generally presents its head to the orifice, and as its whole length is from eighteen to twenty inches, it cannot possibly lie stretched out at full length in a space of only twelve inches long. Hence the foetus is doubled up or flexed in all its limbs as well as its trunk, so that it may be said to rest within the womb in a state of universal flexion. The whole trunk is bent forwards; the neck is so bent forwards as to cause the chin to rest upon or near to the breast which serves to point the apex of the head or vertex to the opening; the arms, forearms, and hands are flexed, as are also the thighs and legs. Doubled up in this way the mass of the foetus is olive-shaped, the cephalic pole being downwards, and the pelvic pole upwards. The drawing (Fig. 16), to which I here refer, exhibits very correctly this flexed state of the child in a vertex presentation.

A vertex presentation is one in which the head-pole presents flexed. If the head-pole should present not flexed it would not be a vertex presentation, but it might be a presentation of the crown of the head, of the forehead, or of the face, and whether one or the other of these three, would depend on the degree of departure of the chin from the breast. The chin in a vertex presentation must be at the breast, because the head is flexed, or bent forward. When the head is not flexed, but on the contrary is extended, it is the crown that presents, or the forehead, or lastly, the face.

A great majority of children in labor present by the vertex, and the most of them direct the vertex to the left side, while the forehead is to the right side of the pelvis; but in these cases the occipitofrontal diameter crosses the pelvis obliquely from the right sacro-iliac synchondrosis to the left acetabulum.

The superior strait is four, four and a half, and five inches in its antero-posterior, its transverse and oblique diameters. The child's head is 3.88, 4.10, and 5.5 in its biparietal, occipito-frontal and occi

pito-mental diameters. The spinal column juts forwards like a half column or pilaster so as to overhang the superior strait like a promontory at the sacro-vertebral angle as well as far above it. Hence it is that the biparietal diameter of the child adapts itself to the short diameter of the superior strait, while the occipito-frontal diameter coincides with one of the longer ones, and so it happens that the head comes into the strait obliquely, or as above said with its vertex to the left acetabulum, and its forehead to the right sacro-iliac junction, thus crossing the strait diagonally.

I say diagonally, for, although it be true that a child may descend through the plane in a direct position, i. e. with its vertex, or its forehead to the pubis, such direct positions are rarely to be met with; and clinical experience shows that, in the immense majority, the head sinks below the plane with the occipito-frontal diameter coincident with the oblique diameter of the upper strait, as in Figure

The foetal head usually descends through the plane of the abdominal strait in flexion, i. e. with the chin to the breast, the vertex being turned towards the left

acetabulum, while the bregma, or upper part of the forehead, points towards the right sacro-iliac symphysis: vid. Fig. 20. The occipitofrontal diameter is probably nearly coincident with the plane of the strait in the beginning of most labors, whence it appears that the occipito-mental diameter must dip its occipital extremity beneath the plane.

In proportion as the presenting part descends lower and lower, the dip of the occipital pole of the occipito-mental diameter increases. It must be so, since the occipito-frontal diameter could not descend hori zontally into a pelvis too narrow for it. That diameter which, by my averages, is 4.10, could not, without a dip or see-saw, sink into the lower part of a pelvis whose transverse diameter, low down in the excavation, does not considerably exceed four inches.

The deeper the head plunges into the cavity, the more strongly is the chin forced against the breast, or, in equivalent terms, the greater the flexion of the head.