It is important to remember that after death the blood leaves the arteries and left side of the heart, and collects in the veins and the right cavities of the heart. Especially does it collect in the vessels of the most dependent portions of the body and of the various organs, so that local congestions may often disappear after death; and again, they may be found at an autopsy where they were not present during life. Especially is this true of the mucous membranes such as those of the trachea and bronchi, and also of the blood in the sinuses of the dura mater.
In making autopsies it is a cardinal rule that all the cavities of the body should be examined, and not alone the one where one might expect to find a lesion. At medico-legal autopsies, the great cavities—the head, the thorax, and the abdomen—should be examined in their successive order from above downward. The reason for beginning with the head is that the amount of blood in the brain and its membranes may be determined accurately; for, if the heart and great vessels of the neck are opened first, the blood will drain away from the brain and local congestions disappear. In pathological autopsies, the opening of the head first is not so important, and often the vertebral column need not be opened at all, for it is a complicated process and takes time; but in medico-legal cases, especially where a question as to the cause of death may arise, and has not satisfactorily been determined, after all the other cavities are examined the vertebral column should always be opened and the cord removed.
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.