BONES OF THE CRANIUM. 1ST 



the mastoid is the stylo-mastoid foramen, for transmitting 

 the facial nerve, or portio dura of the seventh pair. This 

 foramen is the lower aperture of the aqueduct of Fallopius. 

 The styloid process is surrounded by a process at its 

 root, very prominent anteriorly, called the vaginal, which 

 separates the glenoid cavity from the carotid foramen, and 

 foramen lacerum posterius. 



In front and obliquely to the inside of the styloid process 

 is the foramen caroticum leading into a canal, the carotid 

 canal, which is first vertical, and then proceeds forwards, 

 inwards and upwards, and opens within the cranium, by 

 the side of the body of the sphenoid bone. It gives passage 

 to the carotid artery and branches of the sympathetic nerve. 

 In front of the carotid foramen is a rough surface for the 

 origin of the levator palati muscle. By the side of the styloid 

 process is a vertical ridge, within and posterior to which is 

 a deep cavity called the jugular fossa. This, with a corre- 

 sponding one in the occipital bone, constitutes the foramen 

 lacerum posterius, through which passes the eighth pair of 

 nerves and the lateral sinus, the nerves being anterior and 

 separated from the sinus, which is posterior, by the vertical 

 or jugular spine. Upon this ridge is described the opening 

 of the aqueduct of the cochlea. The angle between the 

 squamous and petrous portions is occupied by the spinous 

 process of the sphenoid bone. At this point there are two 

 canals, the one above, the other below, separated by a thin 

 plate of bone; the upper gives origin to the tensor tympani 

 muscle, the lower is the bony part of the Eustachian tube, 

 and both go to the tympanum. The cerebral surface of the 

 petrous portion is divided by a sharp ridge, to which is at- 

 tached the tentoriunr, into an anterior and posterior surface. 

 On the anterior or superior surface is seen a depression for 

 receiving the Gasserian ganglion of the fifth pair of nerves. 

 Near this is a groove leading to an opening about the mid- 

 dle of this surface, called the hiatus Fallopii, which leads to 

 the aqueduct of Fallopius, and transmits the superior branch 

 of the Vidian nerve. This surface is marked by an emi- 

 nence for the superior semi-circular canal, and by depressions 



