This inclination of the sides of the pelvis, due to the position of the planes of the ischia, makes it inevitable for the head, when it happens to present transversely, to spin on its axis and direct its longest diameter at last to the pubis in front and the sacrum behind. If it were not that the ischial planes are thus inclined, there would be no rotation, nor any need for it; but as it is, rotation is almost indispensable. A gestation would hardly go to term but for this inclination without it, the fruit of the womb would continually tend to drop down and be lost, in consequence of the upright attitude of the woman. It makes her parturitions more painful than that of other creatures, but her compensation is found in the Ovidian privilege of the os sublime.

A providential care has been manifested not only in this law of the inclination of the ischial planes, but is equally apparent in the planes of the pelvic canal. The Student has already been advertised that he ought not to adopt the notion that the pelvis has but the two planes; 1st. of the superior, and 2d. of the inferior strait; but rather, conceive of the entire pelvic canal from inlet to outlet as occupied with innumerable imaginary planes. Dr. Tyler Smith, in his Lectures on the Theory and Pract. of Midwifery, Lancet, No. XIX., vol. i. 1856, after remarking that only the upper and lower planes have generally been deemed worthy of particular attention, says, "but it is necessary to consider a third plane situated between the other two, and which may be termed the mid-plane," and he imagines this "mid-plane” to be specially interesting, as being the point "where the rotations of the head are impressed upon it." I have always considered that the flexed head in descending, commences its spiral or rotatory motion as soon as the occipito-frontal diameter begins to rest on opposite sides of the pelvic wall; that it descends rotating, and continues to do so until the crown of the head is pressed against the floor of the pelvis, when the rotation is, or rather, ought to be complete. Hence, I do not admit that there is, within the pelvis, any special plane, whether mid-plane or other that compels rotation. Indeed the whole. trunk of the child, as well as the head, undergoes the spiral or rotatory motion, and it cannot be that so important a portion of the pelvic function depends upon the so-called mid-plane. I present in Fig. 16 an illustration to show that the child is packed up in shape like an olive, and presents its cephalic or head-pole to the opening. If the head must of necessity suffer rotation in its progress, the trunk must do so no less, for it is true that this olive-shaped mass, about to be driven through the pelvic canal, is some twelve inches in length by a little less than four inches in its transverse diameter. For many years

Fig. 16.

past, I have taught at the Jefferson College that the planes of the pelvis are innumerable, and that each and every one of them must be traversed by the descending foetus, at right angles to their superficies, and I am greatly obliged to Professor Carus for his simple and illustrative idea of the Carus curve, which saves me the useless trouble of calculating the places of the planes, and fully answers the demands of the age in the question, What is the axis of the pelvis? a question to which I have taught many thousands of American physicians to answer, it is Carus's curve, which is an arc of a vertical circle projected midway between pubis and sacrum, and which is the track in which

the centre of the encephalon, or of the trunk of the foetus moves in being born. It might well be called the pelvic orbit.

In my view it is pragmatical to pretend to lay down the absolute course of a line that should pass perpendicularly through an imaginary million of imaginary pelvic planes, and always in their exact centres. Such particularity is both useless and impracticable. The operator who adopts the idea of Carus's, or Camper's curve, when in the act of delivering, whether by turning, or with any instrument, has only to keep before him a clear view of Carus's arc, to be sure he is right in his direction of traction, and that, whether he be drawing the cranium through the plane of the superior strait, or through any one of the other planes that are inside of the pelvic canal, or in the extended, produced tube of the vagina, in which sometimes the head is still detained after clearing the lower strait. The accoucheur can always do this operation well, provided he has attained to a correct ideal of the pelvic canal, which he will know is in length equal to the height of the plane of the ischium, or about three inches and a half in all; for that is the measure of Carus's arc of a vertical circle projected within the pelvis midway between the pubis and the sacrum.

I must be allowed here to say a word concerning the plane of the inferior strait, as it is denominated. I myself have already used this word, and shall do so again, and many times, because I cannot escape

from under the tyranny of custom and language. I wish, however, to protest now against the doctrine of a plane of the outlet as taught by most writers and public lecturers. The author just referred to, loc. cit., speaks, as has been seen, of an upper or lower, and a midplane, but there is no such lower plane in fact; on the contrary, the outlet or lower strait is so shaped that there are two planes belonging to it, each nearly an equilateral triangle, and these two planes touch each other at an angle of 90° along the transverse diameter of the inferior strait. The posterior plane descends forwards from the point of the coccyx, its two sides being bounded by the inner lips of the sacro-sciatic ligaments as far as the transverse diameter. The anterior plane descends backwards from the crown of the pubal arch until it meets its fellow, and forms with it, as I said, an angle of about ninety degrees. The child, in being born, displaces these planes, if one might suppose such a thing, pressing the anterior margin of the posterior plane downwards, and dividing the anterior one into two rectangled triangles that yield or open in the middle like winged valves to admit of the child's escape, and then close again. It seems to me that as I have a right to imagine a plane or planes of the inferior strait, there is an attached privilege to conceive of them as valvular.

Ligaments of the Pelvis.-The two symphyseal ends of the pubes are, as I said, united by a fibro-cartilage, passing interchangeably from one bone to the other. The lower edge of this ligament is called the triangular ligament. It serves both to strengthen the joint and to depress the crown of the pubic arch, which arch is thus made cushionlike and lower, and elastic. If the head were pressed immediately against the bony structure, that structure, from its inelastic hardness, would contuse the soft parts of the woman or those of the child; whereas the ligament is of the nature of a soft and elastic cushion.

In dividing the symphysis, there is sometimes, not always, found in the centre of it a very small synovial sac.

The ligaments of the pelvis are of very great importance, for the firmness of the pelvis as an organ for transmitting the weight of the trunk to the lower extremities, and propagating their motion inversely to the trunk and upper limbs, is dependent upon the ligaments. I shall present the reader here with a view of them taken from a distinguished author, who, I hope, will not object to my exhibiting to the American Student a copy of his beautiful drawing. I refer to Dr. Frederick Arnold, from whose Tabula Anatomica, Fasciculus IV. Pars II. Continens Icones Articulorum et Ligamentorum, fol. Stuttgard, 1843, I have taken Fig. 17.

In this figure the letter G is the sacrum; sss the posterior sacral foramina; H the os coccygis, J the right os innominatum, of which a portion has been removed, o the posterior superior spinous process of the ilium, B the greater sciatic notch; 10 the superior ilio-lumbar liga

Fig. 17.

16

ment; 11 inferior ilio-lumbar ligament; 12 superior sacro-iliac ligament; 13 the posterior superficial sacro-iliac ligament; 15 sacro-sciatic ligament: 16 the sacro-spinous ligament; 17 the sacro-tuberous ligament.

From a mere inspection of Dr. Arnold's figures it is evident that the chief ligamentous strength of the sacro-iliac junction depends, 1st, upon the powerful ligaments on the back part of the pelvis, outside of the excavation; and 2d, on the firm cohesion of the two ossa pubis by means of the strong inter-pubic ligament. The auricular or sacroiliac cartilage, which is not represented, is so strong that I have been much foiled in endeavoring, before my class, to tear open the sacroiliac joint by pulling asunder the ossa pubis after I had performed the section of the pubic ligaments: the origin or insertion of the auricular cartilage must be torn out from the bone before it will yield, for the fibres will not break: they can only be torn out by the roots.

Opening of the Joints.-Many people among the mass of society suppose that in every labor the joints become relaxed in order to let

the child pass through the bones; and a good many ladies daily take a spoonful of oil of olives or castor oil, with a view to promote this desirable relaxation, as they esteem it to be. I have known a young thing take the trouble, nightly, to anoint the mons veneris for a long period with lily ointment, to soften the joint.

It is understood, however, by the anatomist, that these joints do not become open and relaxed as a normal effect of gestation, of labor, or of any endermic or therapeutical measures, resorted to for that end. Yet they do, in some persons, relax, to their great injury or inconvenience, and cases of this kind are recorded in the books, and will be met with by most persons extensively engaged in the practice of midwifery.

As to the symphysis pubis, I have on many occasions found it to be quite loosened, and admitting of motion. One of my patients, whom I have succored in many of her confinements, has generally suffered from the relaxation of the symphysis pubis during the several last weeks of her pregnancies. The articulation becomes so loose as to make a very considerable cracking sound whenever she would turn in bed, or walk; and she has been good enough, in order that I might verify the fact, to allow me to cause the motion by pressing with my hands on the opposite spinous processes of the iliac bones, by which means I could cause the two opposite pubes to approach or separate from each other, or ride up and down, passing each other in the direction of the length of the symphysis.

When the patient, in such a state of the inter-pubal ligament, stands on the right foot, the right pubis rises upwards, while the left descends, and vice versa-so that the act of walking is not only attended with pain, but with tottering and uncertainty.

The lady in question gives birth to children weighing ten and twelve pounds, but she has commonly recovered from the relaxation within about forty days after the birth of the child, and her pubic joint then remains perfectly strong and efficient, until, in the next gestation or lying-in, the pressure or the infiltration come to loosen and dispart the bones again.

This lady has been fourteen times pregnant, and has given birth to twelve children at term. The joint did not give way until the sixth accouchement, which occurred October 20, 1833. The child weighed upwards of twelve pounds. The motion of the symphysis was very obvious, and quite painful. She recovered from it, however, and did not feel it again until near the close of a pregnancy, which was concluded on the 12th December, 1835, by the birth of a son. In about a month the articulation was again as firm as ever. A daughter was