THE EXTERNAL EAR. 731 



tragus ; and the projection at the lower extremity of the antihelix is called 

 the antitragus. The fleshy, dependent portion of the pinna is called the 

 lobule of the ear. 



The form of the pinna and its consistence depend upon the presence of 

 fibro-cartilage, which occupies the whole of the external ear except the lobule. 

 The structure of this kind of cartilage has already been described. 



The integument covering the ear does not vary much from the integu- 

 ment of the general surface. It is thin, closely attached to the subjacent 

 parts, and possesses small, rudimentary hairs, with sudoriparous and seba- 

 ceous glands. 



The muscles of the external ear are not important in the human subject ; 

 and excluding a few exceptional cases, they are not under the control of the 

 will. The extrinsic muscles are the superior, or attollens, the anterior, or 

 attrahens, and the posterior, or retrahens aurem. In addition there are the 

 six small intrinsic muscles, situated between the ridges upon the cartilagi- 

 nous surface. The pinna is attached to the sides of the head, by two distinct 

 ligaments and a few delicate, ligamentous fibres. 



The external auditory meatus is about an inch and a quarter (31*8 mm.) 

 in length and extends from the concha to the membrana tympani. Its course 

 is somewhat tortuous. Passing from without inward, its direction is at first 

 somewhat upward, turning abruptly over a bony prominence near the middle, 

 from which it has a slightly downward direction, to the membrana tympani. 

 Its general course is from without inward and slightly forward. The inner 

 termination of the canal is the membrana tympani, which is quite oblique, the 

 upper portion being inclined outward, so that the inferior wall of the meatus 

 is considerably longer than the superior. 



The walls of the external meatus are partly cartilaginous and fibrous, and 

 partly bony. The cartilaginous and fibrous portion occupies a little less than 

 one-half of the entire length and consists of a continuation of the cartilage 

 of the pinna, with fibrous tissue. The lower two-thirds of this portion of 

 the canal is cartilaginous, the upper third being fibrous. The rest of the 

 tube is osseous and is a little longer and narrower than the cartilaginous por- 

 tion. Around the inner extremity of the canal, except at its superior por- 

 tion, is a narrow groove, which receives the greater portion of the margin of 

 the membrana tympani. 



The skin of the external meatus is continuous with the integument cover- 

 ing the pinna. It is very delicate, becoming thinner from without inward. 

 In the osseous portion it adheres very closely to the periosteum, and at the 

 bottom of the canal it is reflected over the membrana tympani, forming its 

 outer layer. In the cartilaginous and fibrous portion, are short, stiff hairs, 

 with sebaceous glands attached to their follicles, and the coiled tubes known 

 as the ceruminous glands. The structure of these glands and the properties 

 and composition of the cerumen have already been described in connection 

 with the physiology of the glands of the skin. 



General Arrangement of the Parts composing the Middle Ear. Without 

 a very elaborate description, fully illustrated by plates, it is difficult to give a 



