4. =Examination of Base of Cranium.= After the section of the brain the prosector returns to the head and examines the basal sinuses (see Fig. 31) by cutting them open with the point of the brain-knife or by using small shears and forceps. When cut open the walls of the sinuses should be laid back for inspection. Ordinarily the _sinus transversus_, _sinus petrosus superior_, _sinus petrosus inferior_, _sinus cavernosus_ and the _sinus sigmoideus_ are opened. The last-named is given especial attention because of the frequency of thrombosis and its involvement from carious conditions of the neighboring portions of the temporal bone. In purulent mastoid inflammation the infection often reaches the meninges by this route. The _carotids_ and the _exits of the cranial nerves_ (see Fig. 31) are then examined. The _hypophysis_ (see Fig. 31) is then removed by making semicircular cuts through the overlying dura mater around the gland and then lifting it out of the sella. This is best accomplished by means of the small scalpel and forceps. It is sometimes necessary to chisel away the overhanging bony parts in order to remove the hypophysis without damaging it. When removed it may be sectioned by a sagittal cut made either to the left or right of the pedicle. [Illustration: FIG. 32.—Incisions for examination of orbit, ear and nose. x y marks line of incision for exposing nasal tract according to method of Harke.] The basal dura is next removed by means of forceps and knife, chisel or dura-forceps. The bones are then carefully examined for fractures, caries, etc. Particularly in cases of middle-ear disease, meningitis, etc., should the dura be removed from the temporal bone and the latter carefully examined.