ORIGIN AND MR Op INSTRUMENTS.
Some time towards the latter end of the century before last, two instruments were invented ; the vectis, and the for ceps.
The Dectif is what the name implies, • lever which is intended to assist the deli very of the child's head. The forceps consists of two levers joined to each other in such a way that the fulcrum of each blade is foundin the opposite half of the instrument.
In employing a lever there are three points to be considered ; the point of ac tion, the moving power, and the fulcrum or intermediate space between the two. In using, then, the vectis, the point of ac tion is the head of the Child. And here it is too obvious to need mentioning, that the force applied b7 the instrument must be equal to the resistance, if not superior to it , and then the mischief may arise to the parts of the child's head so acted up on, producing much injury : the ear may be injured; the lower jaw or zygomatic process of the temporal bone may be broken ; or any part of the surface from the pressure may slough off: these evils are by no means imaginary ; there are various instances recorded of each of them, and that under the hands of the most careful and dexterous men. When an instrument of this sort is used, it is proper to make the hand the fulcrum on which it acts : now if the force required be but small, this may certainly do well enough ; but where great force is requir ed, this is a very bad support ; besides, the bony parts of the pelvis lie so conve nient, that we may rest our instrument on almost any part of it; yet we should recollect, that whatever part we convert into a fulcrum, we injure more or less, • according to circumstances : if we apply it over the symphysis pubis, we press up on the urethra ; or if in other situations, we shall injure the clitoris, or vagina.
Wherever we find the ear, over that part is the application of the instrument to be made. The injury done to the soft parts will be greater in proportion as we attend less to their safety than to that of the perineum. The integuments suffer again, if we attend to the fulcrum, by which we get a lacerated perineum. So that we either cannot use much force with the vectis, or, if we do, it will be to the certainty of doing much mischief. All these circumstances will depend, howe ver, on the smallness of the difficulty to be overcome ; and if there be no great danger, there will not be much difficulty or pressure.
The forceps has many advantages which are of some consequence to mention. The forceps has thinner blades than the vec tis, and one objection against the use of the last instrument is, its bein so very liable to do harm at its point of g pressure; while another objection is, that as the force is applied higher up, so it makes the head flatter in proportion, and in creases its volume in the direction in which it should be lessened. In the next place, if we consider the vectis, we find, that whenever its pressure is applied to the upper part of the pelvis, it must in crease the volume of the head applied to the lower part of the pelvis ; while we know that the forceps, so far from in creasing the size of the head itself, is ca. pahle of compressing the head in such a ,manner as to bring it into a less compass than before ; so much so, that the head included in the blades of the forceps shall altogether occupy less space than was before occupied by the head alone. It may here be objected, yes; but the head is compressed by this means. Yet, grant ing that it is, we know that at the same time the child is able to bear that com pression without the least injury. Be sides, the practice is justifiable upon other grounds than that of the pressure not hurting the child : for supposing that it did hurt the brain, no more force is used than what is necessary to bring the head along the cavity. It is only com pressed to the size of the pelvis, and at any rate it must come through that cavi ty, therefore it must inevitably suffer that compression, whether conducted through by instruments, or forced through by the labour pains of the woman herself. There are cases where the head, being actually too large for the cavity of the pelvis, would never get through by the exer tions of the woman alone. What is to be done here ? if no other resource be at hand, we must open the head : but here the forceps present, to save the child's life by the compression they are able to make. The truth is, that the brain of an infant will bear pressure very well, so that as far as this goes, the forceps may al ways be very safely applied. We see that they do not act by any partial pres sure, and that the action is diffused.