4. _Circumstances to be learnt by Anatomical Dissection._
After the observations which we have already offered upon the subject of wounds, it can be scarcely necessary to urge the necessity of a speedy examination of the more superficial lesions, which are likely to be effaced, or changed in character by the progress of decomposition; “_putredo mutat formam cadaveris et lesionem_.” The deeper wounds may at the same time be inspected, but the greatest care should be taken that they are not extended during the dissection, for unless they be preserved, as far as it is possible, in their natural condition, we shall not be able to establish a satisfactory connection between the external injury, and the internal lesions with which it may be complicated. Having complied with these injunctions, we are to proceed to lay open the cavities. The order in which these operations are to be performed is not of much moment; but let it be generally understood that the discovery of what may appear sufficient to account for death in one cavity, ought never to prevent our proceeding to the investigation of the rest.
_Dissection of the brain and its membranes._—The body having been placed on its breast, and the chin raised and supported by a block of wood, the anatomist must proceed by making an incision over the top of the head, from the root of one ear to that of the other; and then by dissecting off the integuments, so as to invert one flap over the face, and the other over the occiput, he will be able to discover whether the scalp has sustained any injury, as indicated by the presence of abscesses, sinuses, contusions, and extravasations; he will, at the same time, ascertain whether any fissure or fracture exist, or any morbid change has occurred in the bone, such as sponginess, exostosis, caries, or exfoliation. In performing this part of his duty, we trust he will not mistake, as _Hippocrates_[22] confesses he once did, a fracture for a suture, and vice versa. It is not always easy, however, to determine whether a fracture discovered in the cranium, was produced during life. If it should have occurred immediately before the death of the person, there will be found coagulated blood upon the bone and in the fissures; if the individual has survived for some time, there will be marks of inflammation, and perhaps the formation of pus in contact with the skull; but if a fracture has been occasioned in making the dissection, an accident which may occur in the most careful hands, the blood in the fracture will not be coagulated, nor will there be any effusion around the portions. The skull-cap may be now removed; for which purpose the cranium is to be sawed in a circular direction, about a finger’s breadth above the superciliary ridges, and lateral sinuses; the operation must be conducted with great care, or we shall be in danger of wounding the _dura mater_; the bone must be then divided by a few slight strokes with the chissel and mallet. We shall always find a strong adhesion between the inside of the cranium, and the _dura mater_; partly, in consequence of the small blood-vessels with which these surfaces are connected, and partly, from the close application of the fibrous structure of the membrane to the bone, and which will vary with the age of the subject, and the form of the skull; the handle of the scalpel carefully introduced will afford the best instrument for overcoming this resistance, and will not be liable to lacerate the _dura mater_, or to injure the brain. In effecting the separation, the _meningeal vessels_ frequently deluge the whole surface with blood, a circumstance that deserves attention, in as much as their plenitude marks the congestive state of the brain; it shews also that the blood is in a liquid condition, a fact to which some importance has been attached, as it is supposed to occur more particularly in cases of suffocation. The inner surface of the skull may be inspected with the view of ascertaining whether it be carious.