Henry Gray (18251861). Anatomy of the Human Body. 1918.
the basilar portion of the occipital and the posterior part of the body of the sphenoid form a grooved surface which supports the medulla oblongata and pons; in the young skull these bones are joined by a synchondrosis. This grooved surface is separated on either side from the petrous portion of the temporal by the petro-occipital fissure, which is occupied in the fresh state by a plate of cartilage; the fissure is continuous behind with the jugular foramen, and its margins are grooved for the inferior petrosal sinus. The jugular foramen is situated between the lateral part of the occipital and the petrous part of the temporal. The anterior portion of this foramen transmits the inferior petrosal sinus; the posterior portion, the transverse sinus and some meningeal branches from the occipital and ascending pharyngeal arteries; and the intermediate portion, the glossopharyngeal, vagus, and accessory nerves. Above the jugular foramen is the internal acoustic meatus, for the facial and acoustic nerves and internal auditory artery; behind and lateral to this is the slit-like opening leading into the aquæductus vestibuli, which lodges the ductus endolymphaticus; while between these, and near the superior angle of the petrous portion, is a small triangular depression, the remains of the fossa subarcuata, which lodges a process of the dura mater and occasionally transmits a small vein. Behind the foramen magnum are the inferior occipital fossæ, which support the hemispheres of the cerebellum, separated from one another by the internal occipital crest, which serves for the attachment of the falx cerebelli, and lodges the occipital sinus. The posterior fossæ are surmounted by the deep grooves for the transverse sinuses. Each of these channels, in its passage to the jugular foramen, grooves the occipital, the mastoid angle of the parietal, the mastoid portion of the temporal, and the jugular process of the occipital, and ends at the back part of the jugular foramen. Where this sinus grooves the mastoid portion of the temporal, the orifice of the mastoid foramen may be seen; and, just previous to its termination, the condyloid canal opens into it; neither opening is constant.