74 



THE SKELETON 



into canals by the overlying tympanic plate. The lower is the groove for the 

 Eustachian tube [semicanalis tubse auditivse], the communicating passage between 

 the tjanpanum and the pharynx; the upper is the semicanalis m. tensoris tympani, 

 and the lateral apertures of both canals are visible in the retiring angle, between 

 the petrous and squamous portions of the bone. 



The apex of the pyramid is truncated and presents the medial opening of the 

 carotid canal. The latter commences on the inferior surface, and, after ascending 

 for a short distance, turns forward and medially, tunnelling the bone as far as 

 the apex, and finally opens into the upper part of the foramen lacerum formed 

 between the temporal and sphenoid bones. One or two minute openings in the 

 wall of the carotid canal, known as the carotico-tympanic canaliculi, transmit 

 communicating twigs between the carotid and tympanic plexuses. The upper 

 part of the apex is joined by cartilage to the posterior petrosal process of the 

 sphenoid. 



The base is the part of the pyramid which appears laterally at the side of 

 the cranium and takes part in the formation of the mastoid portion. It is 

 described with that division of the bone. 



Fig. 95. — The Left Temporal Bone. (Inferior view.) 



Carotid canal—. 



Tensor tympani 



Levator veli palatini 



Carotid canal 



Tympanic canaliculus 



Canaliculus cochleae 



Mastoid canaliculus 



Jugular fossa 



Jugular surface 



Zygomatic process 

 Masseter 



Articular tubercle 



Mandibular fossa 

 Petro-tympanic fissure 



Tympanic plate 

 Styloid process 

 Stylo-pharyngeus 

 Tympano-mastoid fissure 

 Stylo-mastoid foramen 

 Mastoid process 

 Digastric 

 Occipital groove 



Angles. — The superior angle (border) of the pyramiil is the longest and separates the pos- 

 terior from the anterior surface. It is grooved for the superior petrosal sinus, gives attachment 

 to the tentorium ccr(!l)clli, and presents near the apex a semilunar notch upon which the fifth 

 cranial nerve lies. Near its medial end there is often a small projection for the attachment 

 of the petro-sphonoidal ligament, which arches over the inferior petrosal sinus and the sixth 

 nerve. The posterior angle separates the posterior from the inferior surface, and when ar- 

 ticulated with the oc(;ipi(al, forms the groove for the inferior petrosal sinus, and completes the 

 iugular foramen formed by the temporal in front and on the lateral side, and by the occipital 

 bi-himl and on the medial side. The jugular foramen is divisible into three compartments: an 

 antf-rior for the inferior petrosal sinus, a middle for the glossopharyngeal, vagus and accessory 

 cranial nerves, and a posterior for the internal jugular vein and some meningeal branches 

 from the occipital and ascending pharyngeal arteries. The anterior angle is the shortest 

 and consists of two parts, one joined to the squamous in the petro-sfpiamous suture and a 

 small free part internally whicli articulates with the sphenoid. A fourth or inferior border may 

 be distinguished, which runs along the line of junction with the tympanic plate and is continued 

 on to the rough area below the apex. 



