tones of tlie neat 



The posterior surface shows the internal auditory meatus, 

 which pass the facial and auditory nerves in their arachnoid invest- 

 ment, and the auditory branch of the basilar artery. The facial nerve 

 enters the aqueductus above the sieve-like part of the end of the 

 canal through which the auditory filaments reach the internal ear. 



The styloid process gives origin to small muscles for the pharynx, 

 hyoid bone, and tongue ; the piece of the deep cervical fascia which 

 separates the parotid and submaxillary glands (p. 2) is also attached 

 to it. The temporal bone is developed in four pieces : one for the 

 squamous, one for the petrous and mastoid, one for the tympanic 

 horse-shoe, and one for the styloid process. 



The sphenoid. The body is hollowed out into an air-chamber 

 which opens into the back of the superior meatus of the nose, 

 and on either side is a broad groove for the internal carotid artery 

 and the cavernous sinus (p. 40). The posterior part is connected 

 with the occipital bone by cartilage until the eighteenth year, after 

 which the union is osseous and perfect. The upper surface of the 

 great wing enters into the middle fossa, and is marked by the round 

 and oval openings for the second and third divisions of the fifth 

 nerve, and of the middle meningeal artery and vein. The outer 

 surface enters into the temporal and pterygoid fossas, and the anterior 

 surface forms most of the outer wall of the orbit. 



The lesser wing forms the back part of the roof of the orbit, and 

 supports the frontal lobe. Its posterior border is lodged in the Sylvian 

 fissure of the brain. Between the two wings is the sphenoidal fissure, 

 which transmits the third, fourth, ophthalmic division of fifth, and the 

 sixth nerves, the ophthalmic vein, and some sympathetic filaments. 

 At the root of the process is the foramen by which the optic nerve and 

 ophthalmic artery enter the orbit. 



The external pterygoid process is a wide plate which gives origin 

 to both the external and internal pterygoid muscles. The internal 

 process descends parallel with the vomer, and forms the outer wall of 

 the posterior nares. It ends below in the hamular process, round 

 which the tendon of the tensor palati is reflected. This hook-like 

 process is readily felt in the mouth (p. 107) ; to it are attached the 

 superior constrictor and the pterygo-maxillary ligament. The tensor 

 palati arises from the scaphoid fossa between the roots of the pterygoid 

 processes. 



The ethmoid consists of a vertical plate which enters into the septum 

 of the nose, and of a horizontal, or cribriform, plate which forms 

 part of the anterior fossa of the skull, and on the under surface of which 

 are fixed the lateral masses. The front of the vertical plate extends 

 into the crista galli, between which and the frontal bone is the foramen 

 caecum, transmitting a vein from the nose to the superior longitudinal 

 sinus. At the side of the crista is the slit for the nasal nerve. 

 Through the cribriform plate descend the olfactory filaments, and 





