A System of Midwifery

by Edward Rigby

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 head 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,[81] 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 merely 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 fœtal 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.

Naegelé’s forceps.

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.[82] 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 modification 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 difficulty in locking it than with the English lock: the blades are capable of instant separation, and yet when locked, the firmness of their union is equal to that of a pivot joint.

The handles of the English forceps are pieces of wood or ivory fixed upon each shank below the lock, flat upon the inside, convex externally and furnished with a depression or groove at the lower end for fixing a ligature round them. These handles were probably first introduced by Dr. Smellie, who seems to have borrowed the idea from the forceps of M. Mesnard, for the earlier English forceps, viz. of Giffard and Chapman, terminated in blunt hooks, those of the former being curved inwards, those of the latter outwards, a form of handle which has been retained in the French forceps up to the present time.