The Head.
Make an incision across the vertex of the skull from ear to ear. Dissect the anterior flap forward until within about three inches of the bridge of the nose, and the posterior flap backward to the external occipital protuberance. Examine the internal surface of the scalp for ecchymosis and evidences of injury. A circular incision is then made with a saw through the cranium as far backward and forward as the flaps have been reflected. An incision through the temporal muscle is necessary so that the teeth of the saw may not become clogged by the muscle fibres. When the cranium has been sawed through, a stout hook is inserted under its upper edge and it is removed with a quick jerk. If the dura mater is very adherent to the calvaria, it may be necessary to remove it with the bone, by cutting through it at the level of the cranial incision. Examine the calvaria as also the other bones of the skull after the brain has been removed and the dura stripped off, for evidence of fracture.
Note the symmetry, thickness, and density of the cranial bone, and remember that depressions along the sagittal suture are for the Pacchionian bodies, and are not pathological.
Dura Mater.—The dura mater may be slightly adherent to the bone of the cranium. This is especially seen in old people and does not indicate disease. The Pacchionian bodies are seen along the longitudinal sinus. Examine the internal surface of the dura mater for the presence of clots, tumors, or inflammatory lesions. Open the longitudinal sinus and examine for thrombi. Remove the dura mater by an incision following the cranial incision, the falx cerebri between the anterior lobes being drawn back and divided. Note whether the dura mater is adherent to the pia mater, and the condition of its internal surface.
Pia Mater.—The brain, covered by the pia mater, is now exposed. Note the degree of congestion of the membrane, its adherence, and the existence of pus, blood, or serum on its surface or in its meshes. Remember that a considerable amount of serum may be present within normal limits, especially in cachectic subjects, without indicating disease, but when the serum is so extensive as to raise the pia mater and to depress the convolutions, we have a pathological amount which may be a simple dropsy due to some general cause, or the result of a chronic meningitis. Enough serous effusion in the pia mater to produce a condition which has been called by some writers “serous apoplexy,” I believe never occurs as a primary condition.
Loss of transparency and thickening of the pia mater, especially along the longitudinal fissure, is often seen in old people and does not indicate disease.
Brain.—Remove the brain by raising the anterior lobes with the fingers of the left hand and cutting through the nerves, vessels, and the tentorium as they appear. The medulla is cut as low down as possible, and the brain as it rolls out is caught in the left hand.
After being placed on a clean board or in a large clean dish, it is minutely examined. The average weight of an adult male brain is forty-nine and one-half ounces; of the female, forty-four ounces. Its proportional weight to that of the rest of the body is as 1 to 45.
Lay the brain first upon its convex surface and examine the arteries at the base for atheroma, thrombi, emboli, and aneurisms. Examine the pia mater of the base, especially for the evidences of hemorrhage, tumors, tubercles, and inflammatory lesions. Next turn the brain over on its base, and proceed to open its various cavities and examine its internal structure. Separate the two halves of the cerebrum, until the corpus callosum is exposed. Make an incision downward and outward at the junction of the corpus callosum with the cerebrum, and the roof of the lateral ventricles will be cut through and their cavities exposed. Prolong the incision forward and backward so as to expose the cornua. The size and contents of the ventricles should be noted, as also the condition of the ependyma. The floor of the lateral ventricles being the most frequent spot of hemorrhage, if one is found its extent and the parts involved by it should be noted; especially its relation to the internal capsule.
Transverse incisions (about one-sixteenth of an inch apart) are made through the ganglia seen on the floor of the lateral ventricles. Thus any lesions in the substance of the ganglia will be disclosed. Three or four longitudinal incisions are now made outward into the hemispheres nearly to the pia mater. These will divide the hemispheres into long, prism-shaped pieces held together by the pia mater and a little of the cortex, thus enabling the brain afterward to be folded together, and the relations of lesions to the brain as a whole studied. The third ventricle is now examined by cutting through the fornix and corpus callosum at the foramen of Monroe. Next, the fourth ventricle is opened by a longitudinal incision through the lower portion of the vermiform process; its contents, the condition of its vessels and ependyma noted. Then the floor of the fourth ventricle is divided by transverse incisions one-sixteenth of an inch apart, and careful examination made for the presence of minute hemorrhages: for here is a place in the body where almost a microscopical lesion (hemorrhage) may cause sudden death. Each hemisphere of the cerebellum is now opened by a number of incisions starting from the fourth ventricle and passing outward into its substance. The presence of any tumors or hemorrhage in the cerebellum will now be recognized.
In opening the brain, when clots, areas of softening, tumors, etc., are discovered, their exact location in relation to surrounding parts should be noted and the blood-vessels examined for areas of degeneration or aneurism. This examination can be facilitated by allowing a stream of water to flow over the affected part. This will wash out the affected area and allow the vessels to appear.
Eye.—In rare cases it may be necessary to remove the eye. This can be done by breaking through the roof of the orbit with a saw or chisel and dissecting away the muscles so as to expose the optic nerve and the posterior portion of the organ.