opening of a flower is the result of the turgescence of its tissue, consequent upon its full development. Every one knows that there are flowers whose first opening takes place with great regularity at a particular hour; we have ourselves repeatedly witnessed this in a West Indian species of Amaryllis, the long floral leaves of which became detached from each other, and sprung apart, within a few minutes before or after six o'clock in the evening. Although many vegetable and animal periodicities may be shown to be under the influence of external agencies to a certain extent, yet there is ample proof that they are essentially independent of such agencies, and that they form parts of that cycle of phenomena, of which the whole life of the being, from its origin to its final decay, is made up. We do not see anything more wonderful in the recurrence of certain changes at particular times, than in the progressive evolution of the entire organism. The exuviation of the milk-teeth, for example, in a certain regular succession, and at such uniform times, as to afford one of the best tests of the age of the individual, is a phenomenon which strongly marks the disposition in the human system to the spontaneous severance of a vital connexion which has served its purpose, and to the detachment of the part in which it has ceased to exist.

We have adequate reason to believe that the embryo of warm-blooded animals is extremely regular as to its term of development. Thus, in the common fowl, we may calculate almost to an hour (provided that the eggs have not been detained in the oviduct of the hen) the time when the chick will emerge from the shell. And it is well known that the stages of progressive development in the human foetus afford indications from which its age can be determined, with a pretty close approximation to truth. That the development of the uterine structure goes on pari passu with that of the contained fœtus, appears equally evident from a consideration of its phenomena; especially those attending the formation of the placenta, in which organ there is such a marvellous commingling of parts, formed from two distinct and independent centres of development. Now we see pretty clear indications that the placenta of the fully-developed fœtus is somewhat in the condition of the footstalk of a ripening fruit; that is, that having attained its full evolution as an organ of temporary function, its connexion has a tendency to become dissevered, in virtue of causes inherent in itself alone, and quite independent of external agency. Something of this kind seems to have been recognized by Dr. T. Smith himself, who expresses himself, in his chapter on abortion, to the following effect:

"The placenta has a tendency to become unfit for fœtal respiration towards the end of utero-gestation, when Nature is preparing for the change from branchial to pulmonary breathing. There is frequently observed on the surface of the mature placenta crystals of carbonate of lime, which must tend to interfere with its functions as a respiratory apparatus, and generally, I believe, to facilitate its separation from the uterus. This caducous preparation of the placenta, by the deposition of the salt of lime, is probably connected with the demand for ossific matter in the fœtus; but it must also remind you of the deposite of lime upon the egg of the bird, or of silica in the stems of ripe fruit, to facilitate its separation from the parent tree; or we may compare it to the deposite of earthy salts in the lungs of old age, as preparatory to the death of the individual. It is pretty certain that, in some cases of abortion in the latter months, caused by the death of the foetus, the death has depended on the low respiring power of the placenta, the placental

development having progressed so rapidly as to render the organ prematurely decidous." (p. 145.)

Another indication of the necessity for this maturation is to be found in the difficulty with which uterine contractions are excited by the ergot of rye before the normal time for parturition has arrived. Perhaps the strongest proof, however, that the parturient contraction of the uterus is in some way dependent upon the condition of the placenta, is derived from the phenomena which have been described under the designation of superfætation. In whatever way we explain these phenomena,-whether we regard the two fœtuses as the products of two distinct conceptions,— or whether we regard them as twins, of which one is more advanced in its development than the other, the facts remain the same; namely, that one child may be expelled by the parturient efforts of the uterus, whilst the other is detained; that the uterine contractions do not detach the placenta of the latter; but that pregnancy may continue for many weeks or even months longer, until the second child has attained its full term of development. In some of these cases, it is positively affirmed that the first child presented every appearance of maturity; in others, it appears that an abnormal condition of the placenta was the cause of its detachment. In all, however, it is obvious that the retention of the second fœtus was consequent upon its immaturity; and we do not see how this could influence the uterine contractions, except through the condition of the placenta.

There is another most important indication, that the immediate cause of the supervention of labour is to be looked for in the condition of the attachment of the fœtus to its parent, rather than in ovarian excitement ; namely, that preparatory changes are obviously taking place during the last fortnight, or thereabouts, of gestation. The uterus, as Dr. T. Smith himself tells us, begins to contract more closely upon its contents; and the disposition to relaxation in the soft parts surrounding the outlet of the pelvis manifests itself in the descent of the whole mass. We have no doubt that, during this period, a progressive change is taking place in the placental attachment; for such a change may be easily verified in the placent of many of the lower animals (such as the cat), in which the foetal and maternal portions remain more distinct than they do in the human female, these being separable from each other, as the period of parturition draws near, far more easily than at any previous time. And it is not difficult to understand that the completion of this change, involving (so to speak) the death of the entire placenta, shall be the immediate cause of the supervention of labour; just as we know that premature labour may result from the death or abnormal condition of the fœtus and of the fœtal portion of the placenta. This view affords us a rational explanation of the occurrence of uterine action in cases of extra-uterine fotation, which is considered by Dr. T. Smith as clearly indicating that the exciting cause of labour is to be found elsewhere than in the uterus itself. For if the condition of the placental attachment furnish that cause, instead of the state of the ovary, it will do so equally, whether the placenta be attached to the lining of the uterus, or to that of the Fallopian tube, or to any other organ.-As an additional indication that the exciting cause of labour has its place in the fœtal, rather than in the ovarian, con7-IV.

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nexions of the uterus, we may notice the fact, ascertained by Earl Spencer, that of 75 cows in calf by a particular bull, the average period was 2881 days; none of these having gone less than 281 days, and two fifths of them having exceeded 289 days. That the male parent could produce any modifying influence on the ovarian periodicities of the female, cannot be thought probable for a moment; but that he should influence the term of fetal maturation, must be admitted to be not unlikely.

We have thus fully discussed the chief theoretical questions raised by Dr. T. Smith, in regard to the cause of parturition; because we consider that his claims are put forward in a manner to attract much attention amongst those who are disposed to accept specious novelties without sufficient investigation into their merits; and because we deem it our duty to subject all such claims to a rigorous and searching examination. We would again disclaim any, wish to disparage Dr. T. Smith's merits. He has displayed great ingenuity and acuteness in the manner in which he has built up his hypothesis, and strengthened it with so many props and buttresses, that its inherent weakness may pass unnoticed. And when we come to discuss the practical portion of the work, we shall find that this same ingenuity has led him to originate many useful suggestions, for which he will deserve the gratitude of obstetricians. But in the character of a philosophic physiologist, of which he is obviously ambitious, we are obliged to regard him as having altogether failed, through a want of that comprehensiveness of survey of phenomena, and of logical appreciation of their entire relations, without which no discovery can be established, however ingenious may be the conceptions put forth, and however probable the doctrines advanced.-In order to avoid the possibility of misconception, we shall briefly recapitulate our positions, in such a form as to indicate what we believe to be the true view of the subject, and to point out the chief errors into which we consider that Dr. T. Smith has fallen.

1. The muscular action of the uterus we regard as essentially peristaltic and independent of nervous stimulation. We fully recognise, however, the fact that the induction of this action is often brought about by nervous agency; but we consider this agency as operating, not directly upon the entire muscular structure of the organ (as when a voluntary muscle is thrown into contraction), but indirectly, by exciting its peristaltic movements, as in the case of other organs composed like it of non-striated fibre, and receiving, like it, their nervous supply from the sympathetic system. We altogether dissent from Dr. T. Smith's doctrine, that the parturient contractions of the uterus, when once established, and even its tonic contraction anterior to labour, are excito-motor; because no adequate proof has been given that they are dependent upon nervous agency at all; and because all analogy, as well as the evidence of experiment and pathological observation (so far as they extend), go to prove that they are not. Nevertheless, we would not deny that the parturient actions may be excited in the first instance by nervous agency; it being very obvious, from the phenomena of abortion, that causes originating at a distance, and not capable of acting in any other way than through the nervous system, may bring about these actions. That the uterus may be thus affected through

the nervous system, has long been taught by physiologists and obstetricians; and Dr. T. Smith's chief movement, in supposed advance, is in referring the regular parturient actions of the uterus to this source.

2. Dr. T. Smith maintains that the exciting cause of parturition is to be found in the recurrence of the periodical excitement of the ovary ; which continues during the entire period of gestation, giving a special tendency to abortion at each return; and which, at the eleventh recurrence, acts with such potency as to induce parturition. He assigns no other cause, however, why this eleventh recurrence should be so much more effectual than the rest, than that by this time there is a much greater aptitude to contraction in the uterus itself, and a readiness to be thrown off on the part of the placenta. That this ovarian excitement, acting by reflexion on the uterus through the spinal system of nerves,-the ovarian nerves being the excitors, and the uterine the motors,-is the exciting cause of normal parturition, is, we believe, an entirely original doctrine of Dr. T. Smith's; no others having advanced beyond the mention of the usual coincidence of the period of parturition with the eleventh ovarian nisus. From this doctrine, however, we feel called upon to withhold our assent; because, in the first place, no adequate proof has been afforded by Dr. T. Smith, that the coincidence of the two phenomena is in any way essential; and because, secondly, a number of phenomena, altogether le t out of view by him, afford a clear indication to our minds that the coincidence is not essential, the normal parturient actions of the uterus being entirely independent of the ovarian nisus. We do not deny that abortion may sometimes result from ovarian excitement; but we conceive that this has no special action, and that it is only one out of many causes that may produce the result where a predisposition to it exists.

3. In searching for the real exciting causes of parturition, we conceive that there is ample evidence, both from the analogy of similar phenomena in the lower mammalia, and from observation on the human subject, to justify the expectation that it will be found in the condition of the placental attachment; and we can see no reason why the changes in which maturation consists, and on which, according to Dr. T. Smith, the peculiar efficiency of the eleventh ovarian nisus depends, should not, when complete, be themselves as potent in exciting the first uterine contractions, as he supposes the ovarian stimulus to be.

4. The parturient efforts of the uterus having gradually advanced the presenting part of the child into the vagina, the other expulsor muscles are called into action through the spinal system of nerves; the requisite stimulus being supplied, either by afferent nerves of the uterus itself, as first suggested by Dr. Carpenter, or by those of the walls of the parturient canal, against the several divisions of which the presenting part of the child successively presses, as maintained by Dr. T. Smith. We are inclined to regard the latter as the correct view of the source of the action; but if any merit be due to the idea of the local origin of the stimulus which excites the reflex action of the expulsors, it appears to us that it may be fairly claimed by the first-named author.

Having thus discussed the main subject of the first portion of Dr. T. Smith's treatise, we may now revert to one or two of the minor topics, of which we thought it better to postpone our notice until this should have

been disposed of. In regard to the fatal movements supposed to be felt during pregnancy, our author maintains that, for the most part at least, they are in reality local spasmodic contractions of the uterus. In fact, all his arguments go to prove that there is no such thing as fœtal movement at all; and he does not even attempt to suggest any diagnostic marks by which the true fœtal movements may be distinguished from the uterine. That many of the supposed movements of the fœtus are really uterine, we quite agree with Dr. T. Smith in believing; but that the fœtus is capable of executing reflex movements within the uterus, and that many of its supposed movements are really due to itself, we are equally satisfied. There is no mistaking the form of the infant's foot, which often causes a projection of the uterus in the later months of pregnancy, and which may be distinctly felt when the abdominal parietes are thin; there is no possibility of error when we can feel this withdrawn and pushed out elsewhere, so prominently that we can even count the toes. Nor can there be any mistake when fatal movements are excited during labour by irritation of the presenting part. On the other hand, the spasmodic twitchings of the uterus itself communicate a different sensation to the hand laid over the part; and we can scarcely imagine that any practitioner endowed with the tactus eruditus, and possessed of the knowledge of both sources of movement, can have much difficulty in the diagnosis when either occurs separately. We are disposed to think, however, that the two are frequently concurrent; and that either may excite the other. Nothing would be so likely to excite local contractions of the uterus, as the pressure or impulse of the limbs of the fœtus against its walls; and nothing would be so efficient in calling the reflex mobility of the fœtus into play, as the spasmodic twitchings of the portion of the uterus that might happen to press on any prominent part. We would commend to the attention of Dr. T. Smith, and of our readers, the very interesting papers on the reflex movements of the fœtus, as the cause of its position in the uterus, contributed by Professor Simpson to the recent numbers of the Edinburgh Monthly Journal.'

Active dilatation of the os uteri.-Great stress is laid by Dr. T. Smith upon what he terms a positive dilatation of the os uteri, over and above the mechanical dilatation of this structure by the pressure of the amniotic bag, and the tension exerted on the opening mouth of the uterus by the contractions of the rest of the organ; and upon the reflex nature of this dilatation. Other authors have spoken of a " disposition to dilatation," by which they implied (we suppose) a passive condition of the sphincteric fibres, which caused them to yield before the propulsive force exerted by the active contractions of those of the remainder of the uterus. But Dr. T. Smith considers that the dilatation of the os uteri is itself an active process, the result of an operation of that same reflex function which he has called in to the assistance of the uterus in explaining the other parturient actions. We are unable to appreciate the force of the evidence which has led him to this assumption; a certain hypothesis that other sphincters have a similar power of "active dilatation" being the chief groundwork of his argument. Now we cannot, for our own part, see the slightest proof that the cardiac sphincter, or the sphincter ani, are ever in any condition different from those common to other muscles, namely, a state of contraction more or less powerful, and a state of relaxation more