the stretch and dividing the loose connective tissue holding it by sweeping strokes of the scalpel nearly as far forward as the orbits. After a part of the flap has been freed it is often possible to strip the rest without using the scalpel. For the posterior flap, which should be removed back as far as the occipital protuberance, the scalpel nearly always has to be used.

If the hair is long, the anterior portion can be rolled into the anterior flap over the face and thus protected. The posterior portion is gathered at the nape of the neck, and then a towel is wrapped tightly around the head and neck, extending from the line where the flaps are reflected down. to the shoulders, and is pinned over the lower part of the forehead. In this manner the hair is perfectly protected from being soiled and ample room is left for work.

Of the two methods of opening the skull, the circular and the wedge-shaped, the former makes the better museum preparation, but the latter is in greater use in this country, and has the advantage of rendering the calvaria less likely to slip out of place after the head has been sewed up.

The wedge-shaped incision consists of three cuts, which should be outlined on the periosteum of the skull with a scalpel. The first cut begins just above and behind the left ear, and is carried over the forehead just back of the edge of the hair or over the frontal eminences to a corresponding point above and behind the right ear. The two other cuts begin at each end of the first incision, forming there an obtuse angle, and are carried back to meet in the median line behind at an angle of about 160° a little in front of the occipital protuberance. The temporal muscle on each side is now to be scraped back from the line of incision out of the way of the saw, but is not to be cut off. The holder, if one is used, is attached with a foot in each obtuse angle in the temporal region. If a holder is not employed, the head is best steadied by hands on the calvaria and face. Use towels or cloth to prevent slipping.

Start the incision with the saw over the forehead and extend it back along the line marked out. It is best not to

carry the incision clear through the inner table of the bone, for two reasons: first, on account of the danger of injuring the brain-substance; secondly, because if the inner table or a part of it is cracked through with a chisel and hammer, it can be done without injuring the underlying tissue, and the irregular overlapping fragments of bone thereby formed serve afterward for holding the calvaria firmly and steadily in place.

After sawing along the lines marked out, insert a chisel in the frontal region, and with a quick, sharp blow crack through the rest of the inner table. In like manner insert the chisel in the middle of the other incisions and free the calvaria posteriorly. To remove the calvaria insert the chisel end of the hammer in the incision in the frontal region, and press down with the left hand while swinging the handle around in a horizontal plane.

By means of the powerful purchase obtained the calvaria is easily started. Then catch the hook of the hammer over the calvaria and strip it off. If the dura is adherent to the calvaria, it may be freed by using the point of the closed enterotome to pry it off.

In young children, and sometimes in old people, it is necessary to remove the dura with the calvaria. To do this, cut through the dura with the point of a scalpel along the lines of incision in the skull; then cut the falx cerebri in the median line, both anteriorly and posteriorly.

An infant's skull is best opened by cutting with a pair of scissors through the dura along the sutures (in the longitudinal suture on each side of the falx) well down to the floor of the skull. This gives five bone-flaps which may be turned out like the petals of a flower, leaving the brain uninjured. It is often necessary to cut half of the base of each flap in a horizontal line to aid its being turned out. The falx cerebri must of course be divided anteriorly and drawn back before the brain is removed. In sewing up, the boneflaps are turned in over a bag of sand or sawdust filling the cranial cavity, and are kept perfectly in place by the skin.

In a case of fracture of the skull no cracking with hammer

and chisel is allowable; the calvaria must be freed entirely by sawing. The calvaria should be examined at the time of removal.

The next step is to inspect the dura. Under normal conditions it is not tense in the frontal region, but can be picked up with the forceps or fingers. If the dura is not thickened, the convolutions normally should be visible through it. The longitudinal sinus is opened with knife or scissors and its contents examined. Pacchionian granulations are not infrequently found projecting into it.

To remove the dura, cut through it with scissors or knife along the same lines in which the calvaria was sawn. Turn back each half of the dura and examine the surface of the convolutions and the inner surface of the dura. The convolutions should be distinct and rounded, not flattened, with obliteration of the gyri, as occurs when there is internal pressure.

The Pacchionian granulations are situated along the longitudinal fissure and may grow through the dura and form depressions in the calvaria. There may be apparent adhesions between the dura and pia due to veins passing from one to the other. The dura is still further freed by seizing the two halves anteriorly and lifting them up until the falx is tense at its insertion into the crista galli. Pass a knife in parallel to the falx, on the left side, with the edge forward, as far as the cribriform plate; turn it to the right and cut until the falx yields. Withdraw the knife in the same manner in which it was inserted. Next draw the dura back. It is usually more or less attached along the longitudinal fissure by Pacchionian granulations and by blood-vessels. These may be cut or torn through. Do not cut the dura posteriorly, but let it hang down.

To remove the brain, insert the two fore fingers, or the first and second fingers of the left hand, anteriorly between the dura and the frontal lobes, one on each side of the falx cerebri, and draw the brain gently back until the optic nerves are visible. Ordinarily, the olfactory nerves come away from the cribriform plate without trouble, but sometimes have to

be freed with the point of the knife. With a long, slenderbladed knife divide the optic nerves as far forward as possible while holding the brain back with the left hand. Continue to draw the brain carefully back and divide the cranial nerves

and the carotids. Then draw forward first the left, then the right temporal lobe, and cut the tentorium close to its attachment to the petrous portion of the temporal bone with a sawing motion, using the tip of the knife. Insert the knife. at the side close to the squamous bone, and cut from there

in toward the foramen magnum. Then cut the nerves given off from the medulla oblongata while supporting the convexity of the brain in the left hand.

Lastly, carry the knife as far as possible into the spinal canal, and divide the cervical cord by an oblique incision from each side, severing the vertebral arteries with the same stroke. Better than a knife is the myelotome, because it gives a cross-section of the cord and allows more of it to be removed.

The brain is now to be removed by passing the first and second fingers of the right hand in on either side of the cord, and everting the brain while still supporting it posteriorly with the left hand.

Before proceeding to open the brain it is best to examine the base of the skull, particularly the dura, of which the sinuses should be incised, and the hypophysis cerebri.

If there is a suspicion of a fracture at the base, strip off the dura, so as to give a better opportunity for examination of the bone.

The brain should be weighed before it is dissected. The average weight in an adult male is 1358 grams; in an adult woman, 1235 grams.

External Examination of the Brain.-Place the brain with the base uppermost and with the cerebellum toward the operator. Examine first the pia and the cranial nerves, then the arteries, especially the middle cerebral and its branches on each side in the fissure of Sylvius, for it is here that emboli most frequently lodge. The pia bridging the fissure of Sylvius can sometimes be torn through, but usually has to be cut.

It is important, particularly in cases of obscure cerebral symptoms, to feel gently with the finger-tips all over the surface of the brain for any areas of increased density, because patches of sclerosis may in that way be found which might otherwise be overlooked.

By stripping off the pia-a procedure not often advisable -adhesions over pathological areas can sometimes be found pointing to the lesions beneath, but the pia should not be