THE ORGANS OP HEARING. 393 



the principal fossa, called the concha (a shell), 5, which leads directly 

 into the external auditory meatus, m. In front of the concha, and 

 overlapping the meatus, is a small pointed eminence, generally studded 



Fig. 74. 



Fig. 74. Diagram, showing the parts of the external, middle, and internal ear. in connection with each 

 other, ft, concha of the auricle, m, half section of the external auditory meatus, with its ceruminous 

 glands; it leads from the concha to the membrana tympani. d, is one-half of this membrane, or the 

 membrane of the drum of the ear, which divides the exte-nal from the middle ear. t, the cavity of the 

 tympanum, or drum of the ear, containing three little ossicles; it is also called the middle ear. e, the 

 Eustachian tube, which leads from the tympanum to the back of the pharynx, i, the mastoid cells, which 

 also communicate with the tympanic cavity, s, the semicircular canals, c, the spiral walls of the coch- 

 lea; these two last-named parts, with the vestibule, form the internal ear or labyrinth ; they are lodged 

 and incased in the petrous portion of the temporal bone, p, p. /. the styloid process. 



with hairs on its inner and concave surface, called the tragus; opposite 

 to that is another eminence, the antitragus, and below this is the 

 lobule. The framework of the auricle is composed of a firm elastic 

 cartilage, having nearly the same shape and varieties of surface as the 

 perfect auricle, but it does not extend into the lobule. It is connected 

 with the neighboring parts by ligaments, and is provided with three 

 feeble muscles, named the attollens, attrahens, and retrahens auris. 

 The skin covering the auricle contains sebaceous glands; these are 

 most numerous in the concha. The external auditory meatus, m, is a 

 slightly curved tube, extending from the concha inwards to a mem- 

 branous partition named the membrana tympani, d, which completely 

 closes it at the bottom; it measures about 1J inch in length, and is 

 narrowest in the middle part. The outer half of the meatus has carti- 

 laginous, and the inner half, bony walls; the former is continuous 

 with the cartilage of the auricle. The skin lining the meatus is very 

 thin, especially towards the bottom of the canal, where it is prolonged 

 over the membrane of the tympanum, forming its outer layer: in the 

 cartilaginous part, it is provided with fine hairs, sebaceous glands, and 

 numerous ceruminous glands; the latter secrete the cerumen or ear- 

 wax. 



The middle ear, or tympanum, t, is a small cavity, or chamber, in 

 the temporal bone, containing air, and certain small bones, named the 

 ossicles of the ear, and a few muscles and nerves ; it is placed between 



