CHAPTER I.

THE OPERATION.

In opening the head for a post-mortem examination, let a thick block be placed beneath the occiput, when, after having carefully parted and turned aside the hair, an incision may be made through the scalp, over the top of the head, from ear to ear. The back of the scalpel being placed next the head, the point may be pushed in advance, thus dividing the tissues without danger of injuring the edge of the instrument by bringing it in contact with the bone.

From the loose connection of the tendon of the occipitofrontalis muscle to the periosteum, by the use of the handle of the scalpel, the flaps of the scalp may readily be turned aside, the anterior over the face, the posterior on the back of the neck. The _skull clamp_ may now be applied, which will be of great service in steadying the head while using the saw. Instead of dividing the skull in a circular manner, as is usually done in the dissecting-room, it will be better to start the saw above the frontal eminences and run obliquely down towards the mastoid process, meeting this line by another commencing at the occipital protuberance and carried horizontally forwards, thus giving a wedged form to the portion removed. The advantage of this method consists in our being better able to hold the parts in position as they are replaced, as in the old method, from the readiness with which the parts move upon one another, the calvarium is liable to slide forwards or backwards from its position, thus producing an unsightly ridge across the forehead, which will more or less plainly show through the integument. With young children, a strong pair of scissors may be used instead of the saw in dividing the calvarium.

In using the saw, care should be observed not to injure the dura mater; hence it will be better not to attempt to divide both tables with that instrument, but rather depend upon the chisel or rachitome for breaking away the inner table. To avoid the sound which would attend the use of the iron hammer, which, if heard by members of the family, might excite unpleasant feelings, a billet of wood or wooden mallet may be used; or, these not being at hand, the head of the iron hammer may be muffled with a towel, so as materially to deaden the sounds. The inner table having been divided, the calvarium may be pried off with the chisel, or torn away with the hook on the handle of the hammer. This, from the close adhesion of the dura mater to the bones, will generally require considerable force.

The calvarium having been removed, and the superior longitudinal sinus opened, and the condition of its contents noted, the dura mater, after its careful examination, may be cut through with the knife or scissors in the line of the division of the bone. The membrane may now be lifted up, when adhesions will be found between its under surface and the pia mater, along either side of the falx cerebri. These should not be mistaken for results of inflammation, as they sometimes are, they being simply the points of entrance of the veins of the pia mater into the superior longitudinal sinus. These having been divided, with the falx near its attachment to the crista galli, the whole may be turned back, exposing the brain.

To remove the latter, take away the block from beneath the head, and lifting the anterior lobes of the brain, divide successively the several pairs of nerves as they appear in sight, with also the tentorium on either side, and as the brain falls back into the left hand, the knife may be passed down into the foramen magnum, and the medulla oblongata and vertebral arteries divided, when the whole may be lifted from its position. More or less blood with the _cerebro-spinal fluid_ will necessarily flow off during this operation, to secure which, a bucket should be placed beneath the edge of the table, over which the head should slightly project. In dropsy of the brain, although the fluid is mainly in the ventricles, it may escape during the operation and be caught in the same manner.

The external surface of the brain having been carefully examined, the hemispheres may be sliced off to a level with the corpus callosum, when, by removing the latter, the cavities of the lateral ventricles will be exposed. After a careful inspection of the several objects seen here, the fornix and velum interpositum may be removed, opening thus into the third ventricle. Slices may now be taken off the corpora striata and optic thalami, with deeper portions of the hemispheres, and sections made of the crura cerebri cerebellum and medulla oblongata, thus giving an opportunity of judging of the condition of all those parts.

After the removal and examination of the brain, attention should be given to the _base of the skull_. The lateral and other sinuses should be laid open, the dura mater, as far as possible, torn away, and the bones examined for fractures, caries, abnormal growths, etc.

“_The simplest method for removing the ear_ for the sake of dissection is, after the removal of the calvarium in the usual way, to take out both the petrous bones together by means of two transverse vertical sections, one in front of the two petrous bones and the other posterior to them. The anterior of these sections should pass in a line a little anterior to the anterior clinoid processes, and the posterior in a line through the posterior third of each mastoid process. By means of these two sections, the trumpet-shaped extremity of each Eustachian tube, a portion of the mucous membrane of the fauces, and the whole of each petrous bone, together with the mastoid processes, can be taken out.

“The disadvantage of this procedure is the disfigurement which is apt to ensue from the falling in of the face. To avoid this disadvantage, another mode of removing the ear may be resorted to. This consists in taking out each petrous bone separately in the following manner: The calvarium having been sawn off, an anterior section is to be made in each side in the same line as in the above plan, but extending only as far as the outer part of the body of the sphenoid bone; a posterior section in each side is then to be made, as in the first plan, but not extending farther inwards than the basilar process of the occipital bone. These two sections are to be made with a saw or with a chisel and hammer. The apex of each petrous bone is then to be separated from the sphenoid and occipital bones, and each petrous bone (the outer ear and integument being detached and reflected downwards) is to be drawn outwards, taking care, by inserting the scalpel deeply, to remove as much of the soft parts as possible.

“The organ of hearing having been removed, the dissection may be conducted in the following manner: The auditory nerve in its meatus should be first carefully examined, presuming that a previous inspection has been made of the portion of the brain to which the portio mollis and portio dura nerves are attached. The size of the external meatus having been ascertained by allowing a strong light to fall into it, its anterior wall is to be removed by the cutting forceps.

“The state of the epidermis, the ceruminous glands and secretion, the dermis, periosteum and bone is to be noticed. The outer surface of the membrani tympani is then to be examined; also the state of its epidermoid and dermoid laminæ, its degree of tension, and the amount of motion possessed by the malleus when pressed upon by a fine point. The next step is to ascertain the condition of the guttural portion of the Eustachian tube, to lay open the cartilaginous tube with the scissors, and then to expose the cavity of the osseous portion by means of the cutting forceps. In doing this, the tensor tympani muscle is exposed; its structure should be examined, and if it has not a healthy appearance, portions of it should be submitted to microscopic inspection. The upper wall of the tympanum is next to be cut away by means of the cutting forceps. In doing this, great care must be taken not to disturb or disconnect the malleus and incus, which lie immediately beneath it. After the tympanic cavity has been exposed, the first step is to pull the tensor tympani muscle and ascertain how far it causes a movement of the membrana tympani and ossicles. The incus and stapes are now to be touched with a fine point, so as to ascertain their degree of mobility; the tendon of the stapedius muscle is also to be pressed upon. The condition of the mucous membrane of the tympanum and of the mastoid cells is then to be ascertained, and any peculiarity of the cavity, the existence of bands of adhesion, etc., to be noted.

“The most delicate parts of the dissection, viz., that of the internal ear, must now be undertaken. The cavities of the vestibule and cochlea are to be exposed by removing a small portion of the upper wall of each. Before reaching the vestibule, the superior semi-circular canal will be cut through and removed; the membranous canal should be drawn out and inspected. As the cavities of the vestibule and cochlea are laid bare, it is desirable to see that the quantity of perilymph is natural, as well as its color and consistence. The outer surface of the membranous labyrinth having been observed, it should be opened so as to expose the endolymph and otoliths, portions of all which parts should be removed for microscopic inspection. This having been effected, the remaining membranous semi-circular canals are to be exposed, and the connection of the base of the stapes to the fenestra ovalis carefully examined. The last stage of the dissection consists in removing parts of the lamina spiralis, in examining them microscopically, and in exposing from within, by following the course of the scala tympani, the membrane of the fenestra rotunda.

“The only part which now remains unexamined is the stapedius muscle; in order to expose it, the course of the aquæductus Fallopii, beginning at the stylo-mastoid foramen, should be followed until the base of the pyramidal eminence containing the muscle is reached.”[1]

_The Eyes, with the optic nerves_, may be most conveniently removed for examination, by breaking up the roof of the orbit with the hammer, and, after the removal of the fragments of bone, dissecting away the fat and muscles until the ball is exposed, when, with the scissors, the tunics of the latter may be divided just behind the conjunctival attachment, and the ball removed with the optic nerve. The front portion of the eye being left in position, by filling the cavity behind with a little cotton or paper, any flattening may be prevented, and thus any appearance of loss of parts avoided.

The examination having been completed, the brain may be replaced, the calvarium put in position, the scalp brought over the same and united with stitches, the arranging of the hair effacing all traces of the operation.

THE SPINAL CORD.

For the removal of the _spinal cord_, place the body in a prone position, and make an incision the whole length of the back, over the spinous processes of the vertebræ. Then raise up and turn aside all the muscles with the integument, exposing the laminæ of the vertebræ. The latter may now be divided with the single or double saw, the rachitome or chisel being used to complete the operation, when the laminæ, with the spinous processes, may be removed in one strip, exposing the cord enclosed in its membranes.

The roots of the nerves may now be divided, and the cord, enclosed in its sheath, removed; care being observed not to handle the parts roughly while so doing. The dura mater may now be split open for the examination of the cord. Should it be desired to preserve any portion for microscopic examination, it may be suspended in a solution of bichromate of potass, xx to xxx grs. to the ounce of water, and in a few days transferred to a solution of chromic acid, ij grs. to the ounce of water, where it should remain until sufficiently hardened to be cut into thin sections.

The examination completed, the parts may be replaced and the incision sewed up.