ORGAN OF HEARING. 



553 



and behind by dense fibro-membraneous cellu- 

 lar tissue, in which many ceruminous glands are 

 imbedded. 



The plate of cartilage which forms the an- 

 terior and lower wall of this portion of the 

 auditory passage is of a triangular shape with a 

 fissure running through its base to near the apex. 

 The base is below ; the apex above. The base 

 corresponds to the anterior surface of the mas- 

 toid process. One side is attached to the 

 anterior and lower part of the circumference 

 of the outer extremity of the osseous passage, 

 by dense and strong cellular tissue. The other 

 side corresponds to the base of the tragus. 

 The apex or angle formed by the two sides 

 runs into the upper part of the base of the 

 tragus, and corresponds to the root of the 

 zygomatic process. The angle formed by the 

 base, and that side which is attached to the 

 osseous part of the passage, is extended into 

 a broad pointed tongue, which is fixed into the 

 deep and rough depression at the lowest part 

 of the margin of the orifice of the osseous 

 passage. The angle formed by the base and 

 the other side is continued into the concha. 



The dense fibrous cellular tissue, which 

 completes the passage above and behind, ex- 

 tends from the cartilage of the concha to the 

 upper and posterior part of the margin of the 

 external orifice of the osseous part of the passage. 



What are called the fissures of Santonm, 

 incisurcB Santorinir^ue, are: 1. that fissure 

 extending through the base of the triangular 

 plate of cartilage to near its apex ; and 2. that 

 between the outer margin of the cartilage and 

 the base of the tragus. These fissures are 

 closed by fibrous cellular tissue which, particu- 

 larly over the second fissure, appeared to San- 

 torini to consist of muscular fibres. These 

 fibres have, therefore, received the name of the 

 muscle of the largest fissure, or the muscle of 

 Santorini, m. incisurte inujoris s. Santorini. 

 Haller considered their action to be, by ap- 

 proximating the cartilaginous pieces, to shorten 

 the length of the passage. 



Viewed as a whole, the auditory passage is a 

 canal of an oval calibre. It leads from the 

 auricle to the tympanum, from the cavity of 

 which it is separated by the interposition of the 

 membrana tympani. In front of it lies the 

 joint of the lower jaw, behind is the mastoid 

 process. In the adult its length is about an inch 

 and a quarter, and its direction is at first some- 

 what forwards, then upwards and backwards, 

 and lastly downwards and forwards again. Its 

 lower wall is from one-tenth to one-fifth of an 

 inch longer than the upper. 



The auditoiy passage is lined by a continua- 

 tion of the skin of the auricle. This skin be- 

 comes more and more delicate as it approaches 

 the osseous part of the passage, extremely so 

 where it is continued on the outer surface of 

 the membrana tympani. The skin of the audi- 

 tory passage is covered with fine hairs, and in 

 old persons close to the entrance, hairs like 

 those on the tragus, sometimes of considerable 

 length, are enrooted. 



The skin of the auditory passage is connected 

 to the subjacent cartilage and bone by rather 



dense and sparing cellular tissue. The epider- 

 mis readily separates by putrefaction, and may 

 be drawn out like the finger of a glove, the 

 blind end being the part which forms the outer 

 borrowed layer of the membrana tympani. 



From about a tenth of an inch within the 

 auditory passage to about one-fifth of an inch 

 from the membrana tympani, the lining integu- 

 ment is perforated by numerous small aper- 

 tures, the terminations of the excretory ducts of 

 the glands which secrete the ear-wax. These 

 excretory orifices are most numerous about the 

 middle of the passage, towards the termination 

 of the cartilaginous and membraneous portion. 



The ceruminous glands, glandules cerumi- 

 noste, are small round or oval bodies of a 

 brownish yellow colour, and very vascular. 

 They are imbedded in the areolse presented by 

 the dense cellular tissue which connects the 

 skin of the auditory passage to the subjacent 

 cartilage or bone. 



The ear-wax, cerumen, is, as is known, a 

 thick orange-coloured or yellowish brown viscid 

 substance, of an extremely bitter taste, and 

 somewhat aromatic odour. When first secreted, 

 it is a thin yellowish milky fluid. (See CERU- 

 MEN.) 



The auditory passage, especially in the 

 middle, is usually covered with a more or less 

 thick layer of it. It consists principally of a 

 butter-like fat and albumen in combination with 

 a peculiar animal matter; of a yellow, bitter, 

 alcoholic extractive matter, with lactate of potass 

 and lime and a watery extractive matter. 



In irritation or diseased states of the glands, 

 the ear-wax is changed in its properties, and is 

 thrown out in larger quantities than usual, so 

 that it collects and comes sometimes to fill 

 completely the auditory passage, and thus give 

 rise to dulness of hearing. 



Fig. 258. 



Horizontal section of the auditory passage (dimi- 

 nished). (From Soemmerring ). 



a. Skin of the face in front of the ear ; b. lobule 

 of the auricle ; c. the antitragus ; d. the tragus cut; 

 e. anthelix ; f. helix ; g. anterior part of the osseous 

 auditory passage, cut ; h, h. anterior part of the 

 cartilaginous portion of the passage, cut ; i. poste- 

 rior part of the cartilage of the ear ; A. membrana 

 tympani ; /. section of the mastoid process ; m. 

 dura mater ; n. skin behind the ear. It is seen 

 continued over the auricle, and from that into the 

 auditory passage ; 0. first or greater curve of the 

 auditory passage ; the end of which is directed for- 

 wards ; p. the second or smaller curve, directed 

 backwards , q. third and smallest curve ; at o. and 

 p. are seen the orifices of the ceruminous glands. 



