THE rYMPAXVM 39 



{ Stylo-glossus. 

 To thf styloid })rocess \ Stylo-hyoid. 



^ Stylo-piiaryngeus. 

 To the zygoma Masseter. 



Intrinsic muscles .| «^<^P^^i"^- 



I lensor tym])am. 



To tlie petrosal Levator palati. 



Ligaments : — 



Capsular 1 Stylo-hyoid. 



Interaiticular I of temporo-mandi- Stylo-maxillary. 



Internal lateral | bular joint. Petro-sphenoidal. 



External lateral J 



Ligaments connected with the ear-bones : — 



Anterior ligament of malleus. 

 External ligament of malleus. 

 Superior ligament of malleus. 

 Ligament <jf incus. 



The blood-supply. — Arteries supplying the temporal bone are derived from 

 various sources. The chief are: — 



Stylo-mastoid from posterior auricular: it enters the stylo-mast oid foramen. 



Tympanic from internal maxillary: it passes through the Glaserian fissure. 



Petrosal from middle meningeal: transmitted by the hiatus Fallopii. 



Tympanic from internal carotid whilst in the carotid canal. 



Auditory from the basilar: it enters the internal auditory meatus, and is distri- 

 buted to the cochlea and vestibule. 



Other less important twigs are furnished by the middle meningeal, the men- 

 ingeal branches of the occipital, and by the ascending pharyngeal artery. The 

 s(|uamosal is supplied on its internal surface by the middle meningeal, and ex- 

 ternally l)y the branches of the deep temporal from the internal maxillar}'. 



Note. — The description of the Stvloid Proces.s and of the J]ar-bones is given on pages 

 ri6-68. 



THE TYMPANUM 



The tympanum is an irregular cavity in the temporal bone. At birth it is a 

 recess in the outer wall of the petrosal, partially closed externally by the scjuamosal. 

 When the various elements of the temporal bone coalesce, and the tympanic plate 

 l>ecomes fully developed, then the cavity is completely surrounded by bony walls, 

 except where it communicates with the external auditory meatus. 



The roof, or legmen tympani, is a translucent plate of bone belonging to the 

 petrosal; it separates the tympanum from the middle fossa of the skull. The iloor 

 is the plate of bone which forms the roof of the jugular fossa. 



The inner wall is formed by the external surface of the petrosal bone, and pre- 

 sents the following points for study: — In the angle between it and the roof is a 

 liorizontal ridge which extends l)ackwards as far as the posterior wall, and then 

 turns downwards in the angle ])etween the inner and posterior walls. This is the 

 Fallopian canal; it is occupied by the facial nerve (seventh). Near the roof, but 

 >»elow the Fallopian canal, is the fenestra ovalis, which leads into the vestibule: 

 this fenestra receives the base of the stapes. Below and in front of the fenestra 

 ovalis is the promontory, which contains the commencement of the first turn of 

 the cochlea. In the lower and posterior part of the promontory is the fenestra 

 rotunda ; this, in the recent state, is closed by the secondary membrane of the 

 tympanum. In the macerated Ijone it leads into the sjjiral canal of the coclilea. 

 The promontcjry is also furrowed by some delicate channels (sometimes canals) for 



