178 



THE SKELETON. 



serves partly for the attachment of the Levator palati and Tensor tympani 

 muscles ; 2, the large, circular aperture of the carotid canal, which ascends at 

 first vertically, and then, making a bend, runs horizontally forward and inward; 

 it transmits the internal carotid artery and the carotid plexus ; 3, the aquceductus 

 cochleae, a small, triangular opening, lying on the inner side of the latter, close to 

 the posterior border of the petrous portion ; it transmits a vein from the cochlea 

 which joins the internal jugular ; 4, behind these openings a deep depression, the 

 jugular fossa, which varies in depth and size in different skulls ; it lodges the 

 lateral sinus, and, with a similar depression on the margin of the jugular process 

 of the occipital bone, forms the foramen lacerum posterius or jugular foramen ; 

 5, a small foramen for the passage of Jacobson's nerve (the tympanic branch of 

 the glosso-pharyngeal) : this foramen is seen in front of the bony ridge dividing 



Canals for Eustachian tube and 



TENSOR TYMPANI MUSCLE. 



Bough quadrilateral surface. 



Opening of carotid canal. 



Canal for Jacobson's nerve. 



Aquseductus cochlese. 



Canal for Arnold's nerve. 



Jugular fossa. 



Vaginal process. 



Styloid process. 

 Stylo-mastoid foramen 

 Jugular surface. 

 Auricular fissure. 



STYLO-PHARYNQEUS 



FIG. 141. Petrous portion. Inferior surface. 



the carotid canal from the jugular fossa ; 6, a small foramen on the outer wall of 

 the jugular fossa, for the entrance of the auricular branch of the pneumogastric 

 (Arnold's) nerve; 7, behind the jugular fossa a smooth, square-shaped facet, the 

 jugular surface ; it is covered with cartilage in the recent state, and articulates 

 with the jugular process of the occipital bone ; 8, the vaginal process, a very 

 broad, sheath-like plate of bone, which extends backward from the carotid canal 

 and gives attachment to part of the Tensor palati muscle : this plate divides 

 behind into two laminae, the outer of which is continuous with the auditory pro- 

 cess, the inner with the jugular process : between these laminae is the ninth point 

 for examination, the styloid process, a long, sharp spine, about an inch in length: 

 it is directed downward, forward, and inward, varies in size and shape, and some- 

 times consists of several pieces, united by cartilage ; it affords attachment to three 

 muscles, the Stylo-pharyngeus, Stylo-hyoideus, and Stylo-glossus, and two liga- 

 ments, the stylo-hyoid and stylo-maxillary ; 10, the stylo-mastoid foramen, a rather 

 large orifice, placed between the styloid and mastoid processes : it is the termina- 



