MECHANISM OF PARTURITION.

It sometimes, although rarely, happens in these presentations, that the head does not rest with the chin upon the breast, but the occiput is pressed against the nape of the neck, as in presentations of the face. The passage of the trunk through the pelvis follows, as above-mentioned, as far as the head: this enters the brim with the occiput in advance, and vertex towards one or other ilium. As it advances through the brim into the cavity of the pelvis, it gradually turns more and more backwards, so that when the body is born, the vertex is turned towards the hollow of the sacrum, and the under surface of the lower jaw behind the symphysis pubis.

The diagnosis of nates presentations is not difficult. The pointed and more or less moveable coccyx, bounded at its broader end by the hard uneven sacrum, and in the contrary direction by the anus, will scarcely admit of a mistake. The tuberosities of the ischia may easily be mistaken, for the malar bone of a face presentation, or even a shoulder, can scarcely be distinguished from them, and the external organs of generation become too much swollen and pressed together to give any certain diagnosis; nor indeed can they be examined in this state without considerable risk of injury. The direction of the sacrum, like that of the forehead in face cases, points out the exact position of the child.

Presentations of the nates, although perfectly natural as far as labour is concerned, are far more dangerous for the child than those of the face, for when the head enters the pelvis, if every thing be not favourable for its passing rapidly through it, the cord is so long compressed that the child is almost certainly lost.

The natural position of the fœtus in utero is admirably adapted for its safe passage through the pelvis under these circumstances, and is what we ought to maintain, as far as possible, during labour. The legs are turned upon the abdomen, the arms are crossed upon the breast, the chin rests upon it, the head being bent forwards, so that the whole forms an oval mass. So long as the child advances gradually, the fundus presses firmly upon the head, and keeps the chin close upon the breast; the head therefore enters the pelvis in the most favourable position possible, and the uterus, not having been suddenly emptied of a part of its contents, continues to act briskly, and presses the head so rapidly through the pelvis, that the child is born without having suffered from any serious pressure upon the cord. As however the body of the child diminishes from its pelvis up to the axillæ, it is very apt to be rapidly expelled as soon as the nates have passed the os externum; and if not, it is but too frequently assisted, as it is called, at the very moment when it ought rather to be supported and prevented from advancing too suddenly. When this is the case, the fundus ceases to press upon the head, the chin quits the breast, and as a space is thus left between them, the arms slip into it, and then turn upwards, so that the head not only enters the pelvis in a most unfavourable position, but, to make matters still worse, it has an arm on each side of it; at this critical moment the uterus, from having been suddenly emptied, ceases to contract, and the head remains so long in the pelvis that the child has no chance of escaping with its life.

Where the child has descended gradually, and the arms have advanced with the breast into the pelvis, if the cord be considerably upon the stretch,

a portion should be pulled gently down in order to relax it, and we should endeavour as far as possible to guide that part of it which is within reach towards one of the sacro-iliac synchondroses, being less liable there to suffer from pressure. One or two fingers should be introduced to bring down the arms, which are now coming into the lower part of the hollow of the sacrum: they should be hooked down by the bend of the arm, in order to prevent the humeri from sticking across the passage. When this has been effected, the shoulders follow as the head descends through the pelvis. The body of the child should now be wrapped in warm flannel, and two fingers passed up towards the face: the lower jaw must not be trusted to in bringing the head through the pelvic outlet and os externum, for it may easily be broken: the fingers should be applied, one on each side the nose, and the chin depressed as much upon the breast as possible, by which means the head will come in a much more favourable direction, and pass readily.

In no case is so much mischief done by impatient interference as in presentations of the lower end of the child. This is still more so in footling cases, for here the soft parts are not so well dilated as in nates presentations, where the child comes double: hence the fact, that presentations of the feet are easier to the mother, but more dangerous to the child. In either case, the passage of the head through the pelvis must ever be attended with considerable hazard; for if it be delayed beyond a short time, the child's death is certain. "The more gradually the nates and body of the child are expelled, the quicker will its head pass through the pelvis, and the better will be its chance of being born alive." (Obstet. Memorand. 2d ed.) Hence, therefore, if the pains are slow at this moment, it will be desirable to rouse them with a dose of ergot: and if the child gives a convulsive twitch, the forceps ought instantly to be applied. The result of Professor Busch's practice in the lying-in hospital at Berlin shows, that by the timely use of the forceps a large majority of children may be saved. For the same purpose, the nurse should be instructed to have a warm bath in readiness, with some spirit, &c. for resuscitating the child the moment it is born.

The numbers which we subjoin are taken from the cases in the Dublin Lying-in Hospital, under the late Dr. Joseph Clark and Dr. Collins, from the private practice quoted in Dr. Merriman's Synopsis, and from the General Lying-in Hospital.

Of 71,578 labours, the nates presented once in every 78 cases, and the feet once in every 1083. Of the nates cases the child was born dead in the proportion of 1 to 3.8, and in the footling births 2 to 2.8.

DESCRIPTION OF THE STRAIGHT AND CURVED FORCEPS.-MODE OF ACTION.-INDICATIONS.-RULES FOR APPLYING THE FORCEPS.-HISTORY OF THE FORCEPS.

BEFORE describing the various species of dystocia, or faulty labour, it will be necessary to consider the different means with which the increasing experience of years has furnished us, of giving artificial assistance in such cases. These may be brought under two heads, first, where delivery can be effected with safety to the mother and her child; secondly, where this can only be effected at the expense of the infant's life. Under the first head come the forceps, turning, the Cæsarean operation, and artificial premature labour; under the second are craniotomy or perforation, and embryotomy.

Of these the forceps is by far the simplest and safest means of artificial delivery, and is therefore an operation which should always be had recourse to in preference to any of the others wherever it is possible.

The forceps is the simplest imitation of nature, for in fact it is nothing more than a pair of artificial hands introduced one on each side the head. It is impossible to define any precise limits of pelvic contraction, within which the forceps can, or beyond which it cannot, be safely applied, for the difference in the size and hardness of the child's head, and in the condition of the soft parts, will greatly modify the degree of resistance to the progress of the labour: hence the attempt to fix the exact degree of contraction beyond which the forceps becomes inapplicable is quite impracticable, as in some cases we might be led to make a trial of it where it would be quite improper, and in others have recourse to the perforator where a cautious application of the forceps would have been attended with success. For the farther consideration of this subject we must refer to the chapter on DYSTOCIA PELVICA.

The forceps consists of three parts-the blades, the lock, and the handles.

The blades of the present forceps are not solid, but are merely elongated bows of polished metal, by which they are not only rendered much lighter, but allow the most prominent parts of the head to project between them, and thereby take up no additional room when introduced into the pelvis. In the simplest form, viz. the straight forceps, the blades have only one curvature for adapting them to the convexity of the head. The degree of curve varies a good deal in different instruments: the greater the curve the more firmly will the blades hold, because they act more or less as blunt hooks, and do not require much pressure upon the head for the purpose, but on the other hand, they are more difficult to introduce; whereas, blades which are slightly curved can be applied with greater ease, but require much more pressure upon the head in order to hold fast.

It has been a general rule with almost every modification of forceps, that the greatest distance between their blades should not be less than two inches and a half, for as this is the breadth of the basis cranii in the fœtal head, it would be impossible to compress the head beyond this extent. The form of the bead curvature will determine the situation of the point where the blades are most distant from each other in some forceps it is about one-third the length of the blades from their extremities; in some it is nearly equidistant; whereas, in others it is nearer to the lock; the medium between these extremes is the best. The extremities of the blades ought to be at least half an inch apart: in this country they are usually somewhat more; on the Continent they are much less, being rarely more than one or two lines asunder. The fenestræ, or open spaces in the blades, should be wide and ample, for not only are the projecting parts of the head allowed to protrude between them, but the pressure of the blades is diffused over a larger extent of surface: this is remarkably seen in the forceps of the late Dr. Hopkins and that of Professor Davis, both of which are extensively used. It is also important that the edge at the extremities of the blades should be well rounded and not too thin; it is thus less liable to catch against corrugations either of the vagina or fœtal scalp. The greatest breadth of the fenestræ is generally towards the extremities of the blades; in some, their edges are parallel; whereas, in those of Drs. Orme and Lowder, the greatest breadth is near the lock: upon the whole, an oval-shaped fenestra is the best; for it can be easily introduced, and has the advantages of a wide blade.

In 1751 and the following year, another curve was given to the blades of the forceps by the celebrated M. Levret of Paris, and by the equally distinguished Dr. Smellie of London, by which the instrument was adapted to the curve formed by the axes of the brim, cavity, and outlet of the pelvis, and by which the head could be seized much higher in the pelvis than by the straight forceps. Each have an equal claim to the merit of having invented this "pelvic curvature," as it has been called: the priority of the invention is perhaps due to Levret; but as he made a secret of it for some years, it is impossible to ascertain the precise fact. The pelvic curve, as it is called, is especially adapted to the long forceps, which thus becomes an instrument of very considerable power. Numerous modifications of these curved forceps have since been made, but they are mere

* Madame La Chapelle calls this the courboure des bords, to distinguish it from the head curvature, courboure des faces (p. 61.)

ly varieties of the original ones invented by Smellie and Levret, which have become the national instruments of their respective countries.

Perhaps the greatest improvements in the blades of modern times is seen in the forceps of Dr. Hopkins, above alluded to: the head curvature forms an elongated oval, admirably adapted to the form of the foetal head when considerably compressed during a difficult labour; and, from the great breadth of the fenestræ, the pressure of the blades is applied over a large extent of surface; the pelvic curve is but slight, being greater on the posterior edge of fenestræ than on the anterior; the blades themselves are thin, their inner surface flat to ensure a firmer hold, their outer surface slightly rounded in order to be introduced with greater ease; and for a similar reason the edges of their extremities are somewhat thicker and carefully rounded in a peculiar manner.

The lock of the modern English forceps consists of two deep grooves, into which the shank of each blade mutually fits, so that the two blades are fixed upon each other merely by the pressure exerted upon the handles. In former times the blades were united together by a pivot, which could screw and unscrew at pleasure. This was abandoned by Chapman, who published the first work in English on operative midwifery.* He found that the forceps held better without the pivot than with it; and from what we have brought forward elsewhere (Med. Gaz. Jan. 8, 1831,) there can be little doubt that he invented the lock which is now generally used in this country. Chapman's forceps was adopted in France, prior to this improvement in its lock, especially by Gregoire, and has retained the original pivot lock which now forms one of the most distinguishing marks between the French and English forceps. Although the pivot forms by far the firmest lock, for the blades can never slip from each other, still the

difficulty in locking, and also in

separating, the blades at a moment's

notice, render it much inferior to the

English lock. An ingenious modi

fication was invented by the late

Professor Von Siebold of Berlin, but the most perfect lock is that of Professor Brüninghausen of Würzburg, first introduced by ourselves into this country, and commonly known among the instrument-makers under the name of Professor Naegelé's forceps. The shank of one blade has a semicircular indentation, which, at the moment of locking, fits into a fixed pivot in the other: this, therefore, combines the advantages of the French and English locks. We can safely affirm, from extensive experience for many years, that there is even less diffi

A Treatise on the Improvement of Midwifery, chiefly with regard to the Operation: by Edmund Chapman, 2d edit. 1735.