THE EAR 



1537 



addition to these sebaceous glands, there are convoluted tubular 

 glands, similar in structure to sweat-glands, and called the cerumi- 

 nous glands, which secrete the ear-wax. 



Blood-supply. — The arteries are derived from the posterior auri- 

 cular of the external carotid, the deep auricular of the first part of 

 the internal maxillary, and the anterior auricular branches of the 

 superficial temporal. The veins follow the course of the arteries. 



Lymphatics. — These pass to the mastoid glands and to the parotid 

 lymphatic glands. 



r- Kerves. — (i) The auricuio-temporal nerve furnishes two branches 

 io the meatus, upper and lov/er, which enter it by passing between 



Upper Part of — r-^ 

 Helix t ^- 



Extemal T.igamfiit of the MalleiE 

 Incns 



Semidicolar Caoak 



CoDcfaa 



External Auditory 

 Meatus 



Malleus 



Vestibule 

 ,/ Cochlea 



Tympantun 



Tensor Tympani Muscle 

 Apex of Pet. Poriion 

 of Temporal Bone 



. —Anterior Lig. of 



the Malleus 



Internal Carctfd 



Artery 



Tip of Styloid Process of 

 Temporal Bone 



Membrana Tympani 



Fig. 643. — General View of the Right Organ of Hearing (after 



HiRSCHFELD AND LeVEILLE). 



(The External Ear and Middle Ear are seen in section). 



the cartila^ginous and osseous walls. The upper branch furnishes 

 twigs to the skin over the upper part of the membrana tympani. 

 (2) The auricular branch (Arnold's ner\-e) of the pneumogastric 

 supplies the skin of the osseous part of the canal over its lower 

 and back part, and also the skin over the lower part of the mem- 

 brana tympani. 



Early Condition of the Meatus.^- At birth the osseous part of the 

 canal is represented merely by the tympanic annidus and a small 

 portion of the squamous part of the temporal bone. It is con- 

 nected by fibrous tissue to the cartilaginous framework of the 

 auricle, and within this fibrous tissue the osseous canal becomes 

 formed by two outgrowths from the tvmpanic annulus. 



97 



