7th. The mind exercises a remarkable power over the phenomena of hysteria; in rare instances causing paroxysms of the spasmodic form of the disease, by a mere act of volition, and in other cases sufficing to effect, or powerfully to aid in effecting, a cure; facts which seem to prove, that hysteria is as purely and unequivocally an affection of the nervous substance as, perhaps, any disease which could be named.

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PART II.

THE BONY PELVIS CONSIDERED OBSTETRICALLY.

The simplest example of parturition is the birth of an acorn, when it falls ripe from its cup. In the lower grades of animated being, the process is an affair almost as simple as this, as I might show, did I feel myself at liberty to do so but I refrain from entering on a field which is both extensive and foreign to the object I have in view, viz. a passing glance at the circumstances of the viviparous quadruped and woman, with their bony pelvis, in reference to the parturient act.

Some, perhaps, may be ready to imagine that oviparous animals cannot, in any way, interest the student of comparative parturition; that such only as expel from a uterus their young, already formed and alive, can, in the nature of things, have difficulty in parturition. The fact is otherwise. Ovipari may have difficulty, owing to certain of that class possessing a perfect pelvis; while some viviparous animals, destitute of a pelvis, are exposed to no kind of obstruction. This naturally suggests, that a bony pelvis is necessary, in general, to the occurrence of seriously impeded parturition.

But vertebrated animals only can have a pelvis; and, of this description, the biped and the quadruped alone need it. Certain fishes, as the haddock, it is true, have a slight framework of bones, affording attachment to the ventral

fins, supposed to resemble a pelvis; but the resemblance is very faint. This word pelvis occurs so frequently in books of midwifery, that most learners are led to regard the bony pelvis as, essentially, a constituent part of the parturient organs. Far from this, it is merely a circle of bones, more or less complete, projected from the spine, to afford attachment for the lower or the hinder extremities, as the animal happens to have two or four feet. No animal, unless it moves upon two or upon four limbs, is endowed with a pelvis. Several mammalia, as the cetaceæ, have no pelvis; numbers of the ovipari, as the tortoise and the crocodile among quadrupeds, and the ostrich among birds, have this part of the skeleton perfectly formed. And, lastly, several species of quadruped mammalia either have an imperfect pelvis, open in front, as the anteater; or so small (as the mole, the shrew, and the seal), that the vagina passes in front of the pelvis.' It is evident, therefore, that in certain mammalia, a pelvis cannot be a cause of difficult parturition; while, on the other hand, it may in the ovipari. In the museum of the late Mr. Fawdington was the skeleton of a female tortoise, which died from difficulty in laying an egg, a fact ascertained by dissection. The animal, in seeming health, suddenly died, from no obvious cause. On cutting open the cloaca, Mr. Clough discovered an egg firmly impacted in that passage, where it had caused inflamma

1 I have never been able to procure a female seal, so as to ascertain the fact here asserted; but I cannot imagine, looking at the size and figure of the pelvis of this animal, that it gives passage to the vagina; unless, indeed, the bones open at the end of pregnancy, as we shall find happens in the guinea-pig; but this I do not suspect.

tion terminating in abscess. The impediment to the expulsion of the egg existed at the outlet of the pelvis, the axis of which, owing to the overlapping of the shell, forms an angle with the axis of the brim, as in the human subject; affording the only instance that I know, in brute animals, of the axis of the outlet deviating from that of the inlet. In the ostrich it is quite conceivable that, were an egg to be of more than ordinary size, (a circumstance, of course, unlikely to happen,) it might suffer arrest, in passing through the strong and complete pelvis of that bird. And here I may mention, that both Blumenbach and Carus speak of the ostrich as the only bird whose pelvis is closed by a complete junction of the ossa pubis; whereas, in Mr. Fawdington's museum, there was a beautiful skeleton of the brown cagle (falco fulvus) having the ossa pubis closed, in the manner of the ostrich.

The form of the superior aperture of the pelvis differs considerably in the different mammalia which possess this part of the skeleton in a complete form. In most, it is a long opening, whose plane, in reference to the spine, is highly oblique; but in heavy animals, as the elephant, the obliquity is lost, and the plane presents nearly a right angle with the spine. The obliquity in question, in whatever degree it exists, does not, as in the human pelvis, affect the axis of the brim, which, in all brute animals, is nearly parallel with the spine. In woman, the dimensions of the brim, in every direction, are greater than in any other animal of similar size; and there is a further difference also: the longest line which can be drawn in the brim is from side to side. This measurement is, in most instances, reversed in the brute; the sacro-pubal diameter being longer than the transverse.

In animals which occasionally stand erect, as the bear and the ape, the transverse is found to be greater in proportion to the sacro-pubal diameter than in other quadrupeds; but still the distinctive character of the animal brim is preserved even in them. In the dog, I have found that the two diameters are the same. It is important to notice that the form and dimensions of the fœtus, in all animals possessing the complete bony pelvis, have relation to the figure and dimensions of the inlet. In other words, there appears to be a natural adaptation in the fœtus to the bony passage through which it is destined to enter the world.

In the human pelvis there is a defined outlet, the axis of which is not the same as the axis of the brim, the two meeting at an obtuse angle; whereas, in the brute, the axis of the brim and of the outlet, as far as the bones are concerned, is, as I have before remarked, nearly the same. In fact, from the sacrum, in nearly all animals, being on a line with the spine, and there being no coccyx, but a flexible chain of bones instead, the posterior opening of the pelvis is large and free. We are not to imagine, however, that the axis of the bony outlet is identical with the axis of the vagina, and os externum in brutes, any more than it is in women. So far from that, the brute fœtus, in its passage through the pelvis, and thence through the os externum vaginæ, describes a curve not quite so great, but approaching nearly to that on which the human foetus moves in labour. And this will be obvious, when we reflect, that although the vagina and rectum are closely adherent high up, the former separates from the rectum, turns forward to reach the pubis, and, consequently, has a very considerably longer course than the other. In some animals, for example, the rat, the