An elementary treatise on human anatomy / by Joseph Leidy.

  • Joseph Leidy
Date:
1889
Catalogue details

Licence: Public Domain Mark

Credit: An elementary treatise on human anatomy / by Joseph Leidy. Source: Wellcome Collection.

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    mari^in of tho occipital foramen. Its anterior extremity ends in a quadrate rough surface, which, previous to ankylosis, is connected with the sphenoid bone by cartilage. The lateral borders of the process join the pyramid of the temporal bone. The lower surface is transversely convex, and is sometimes and variably produced in a feeble median ridge,' which gives attachment to the pharynx. On each side, the sur- face is marked by the attachment of the prerecti muscles. The upper surface forms a smooth concave gutter, the basilar groove,^ which slopes downward to the occipital foramen, and accommodates the medulla oblongata. At the lateral margins it is marked by a shallow furrow for the infrapetrosal sinus. The occipital plate ^ encloses the back part of the cranial cavity in the interval of the parietal bones and the mastoid portion of the temporals. The upper borders^ from the lateral angles converge to the superior angle, and are remarkably jagged for sutural union with the parietal bones; the lower borders,® converging downward and forward, are less rugged than the former, and articulate with the mastoid portion of the temporal bones. The external surface is convex, and forms the prominent back part of the skull. Near its centre it presents a variably produced and roughened eminence, the occipital protuberance,® from which descends to the occipital fora- men a slight ridge, the occipital crest,’ both giving attachment to the nuchal ligament. From the protuberance another ridge, tho superior curved line,® arches outwardly on each side to the lateral angle, dividing the surface into two portions, of which the upper is more prominent and evenly convex, and is covered by the scalp. The lower portion is further divided by the inferior curved line,® which runs nearly parallel with the former. The curved lines and surfaces below them give attachment to muscles of the neck, the im- pressions of which are commonly most marked in vigorous muscular subjects. The internal surface of the occipital plate is divided into four shallow concave recesses, of which the lower and larger are the cere- bellar fossae, for the reception of the hemispheres of tho cerebellum; and the upper ax’e the cerebral fossae, for the accommodation of the hemispheres of the cerebrum. The fosste are defined by a median fore and aft and a horizontal ridge, which together form the occipital cross, and produce at their conjunction the internal occipital protu- berance.'® To the upper arm of the cross is attached the cerebral falx, and it is impressed, usually to one side, with a groove, which ' Crista basilaris ; pharyngeal tubercle. ® bupraoccipital; occipital portion ; squama. ® Margo mastoideus. « External oc. post. * Linea semicircularis superior. Eminentia cruciata. * Sulcus basilaris. ‘ Margo lambdoideus. ’ Crista occipitalis externa. * L. s. inferior. ” Sulcus sagittalis.
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