186 BONES OF THE CRANIUM. 



it the capsular ligament of the lower jaw, and gives 

 passage to the corda tympani nerve, the laxator tympani 

 muscle, and the processus gracilis of the malleus. 



The mastoid, so called from its resemblance to a nipple, 

 is situated at the posterior and inferior part of the bone. 

 It is a rough and depending process, having on its internal 

 aspect two grooves the one for giving origin to the digas- 

 tric muscle the other, a little posterior, transmits the oc- 

 cipital artery. The outer surface of this process gives at- 

 tachment to the sterno-cleido-mastoideus muscle; on the 

 posterior part of this process is generally seen the mastoid 

 foramen, for transmitting the mastoid artery and vein. 



FlG> 4L . The cerebral surface of this 



process is concave, and deeply 

 grooved for lodging the lateral 

 sinus. The third or petrous 

 portion, named from its stony 

 hardness, is situated between 

 the squamous and mastoid, 

 and proceeds forwards and 

 inwards into the base of the 

 cranium. Its/orm is triangu- 

 lar, with the base posterior, 



and presents three surfaces, one external or inferior, and 

 two internal or cerebral. 



On the inferior surface are noticed the following points : 

 first and most prominent, the styloid process, a long, slen- 

 der projection, sometimes two inches in length, giving at- 

 tachment to the three styloid muscles and two ligaments. 

 Behind and at the root of this process, between it and 



FIG. 41 represents the cerebral surface of the Temporal Bone. 1 Squamous 

 portion. 2 Mastoid. 3 Petrous portion. 4 Groove for the middle meningeal 

 artery. 5 Edge of squamous suture. 6 Zygomatic process. 7 Digastric 

 fossa. 8 Occipital groove. 9 Groove for lateral sinus. 10 Superior petrous 

 sinus. 11 Opening of the carotid canal. 12 Internal auditory foramen. 13 

 Aqueduct of the vestibule. 14 Styloid process. 15 Stylo mastoid foramen. 

 16 Foramen caroticum. 17 Spine dividing the jugular vein from the eighth 

 pair of nerves. 18 Vidian foramen. 19 Where the levator palati and ten- 

 sor tympani muscles arise. 



