6. =PREPARATION FOR THE AUTOPSY.= Permission having been obtained, the autopsy should be performed without delay. It is very important that the examination should be carried out before the body has become cold, if any thorough microscopic study of the tissues is to be made. Changes in the finer structure of cells and nuclei quickly take place, and certain tissues, such as parts of the nervous system, the medullary portion of the adrenals, the pancreas, mucosa of gastro-intestinal tract, etc., within an hour or so after death are usually no longer fit for microscopic study. In all cases, therefore, it is best to make the autopsy as soon as possible after death, that is, as soon as positive signs of death appear. In the majority of cases this takes place within an hour, and the most favorable time for the performance of the autopsy falls within one to three hours after death. Under certain circumstances it may be necessary to make the examination sooner, but for various reasons the operation is very repugnant when performed within the first half-hour after death. For ordinary purposes an autopsy performed within twelve to twenty-four hours is usually satisfactory. Occasionally it becomes necessary for medicolegal purposes to examine a body some days, weeks, or even months after death and burial. [Illustration: FIG. 19 Bone-Forceps] [Illustration: FIG. 20 Bone-Nippers] [Illustration: FIG. 21 Probe] [Illustration: FIG. 22 Blow-Pipe] The body should not be frozen if microscopic studies are to be made. When the autopsy is delayed cold storage just above the freezing point produces less change in the gross pathologic picture, as well as in the finer structure. No embalming fluids, injections, punctures, etc., should be allowed, and undertakers should be instructed not to do these things until after the question of autopsy has been decided and the operation completed. If the use of an embalming fluid becomes necessary, formalin, not stronger than a ten per cent solution, should be advised, as it does not damage the tissues and hinders but little the operations of the autopsy. Strong solutions, as found in the usual embalming fluids, render the tissues stiff and hard and cause color changes, while the strong vapors are very unpleasant to the obducent. The use of arsenical embalming fluids or preparations should be wholly discountenanced. When it is desired to study the mucosa of the stomach or intestine, it may be fixed soon after death by the introduction of a fixing fluid into the stomach or intestine by means of a tube and pump. Finally, instructions should be given that the body shall not be dressed for burial until after the autopsy.