THE SENSES. 273 



in the transverse section, and passes from the base of the auditory 

 concha horizontally to the membrana tympani, that is, from without 

 inwards and from behind forwards. Close to the entrance it makes 

 a bend, the curve upwards (whenever we wish to see to the end of 

 the auditory passage, the centre of the auricle must be drawn up- 

 wards and backwards). The entrance is oval beset with hairs, 

 bounded before by tragus, behind by the crescentic crista of the 

 concha. The internal opening circular, directed obliquely from 

 above downwards and from without inwards, and closed by the 

 tympanic membrane. The narrowest place is found at the bend, 

 the widest at the junction of the cartilaginous and osseous parts. 

 Superior wall, ten lines, inferior, thirteen, posterior, ten and a half, 

 anterior, twelve and one third long. 



a. The osseous portion (seven to eight lines long) lies on the basis oss. 

 petrosi, is in' children made up by the annulus tympani, of which a groove 

 remains behind (sulcus tympani}, and which is interrupted at the superior 

 boundary. 



b. The cartilaginous portion (five lines long) is attached by fibrous uniting 

 tissue with the toothed border of the osseous portion, forming, besides, the 

 superior wall which is attached to the proc. zygomaticus. Its inferior longer 

 wall is properly a continuation of the trap*s, from which, by incomplete 

 fissures (incisur<e Santorini), two C -shaped pieces are separated (like the 

 trachea), which are approximated by interposed muscular fibres. The poste- 

 rior wall is connected with the Concha. 



The external integument, which is continued from the external ear upon the 

 interior of the auditory passage, is always more delicate, proceeding inwards, 

 is from the commencement beset with stiff, then with fine hairs and cerumin- 

 ous glands (gl. ceruminosce), and forms internally a closed cylinder, since it 

 terminates upon the tympanic membrane. The glandules are numerous, 

 especially in the centre (some thousands upon a square line.) 



The cerumen is very bitter, partly soluble in water, containing a yellow oil, 

 albumen, and salts of lactic acid. It becomes thickened by the evaporation 

 of its watery elements. 



Vessels: branches of Art. auricular. poster, and profunda. 



Nerves : branches ofauricul. anter. from ram. 3 trigemini and auricul. n. 

 vagi. 



508. 3. The drum of the ear, membrana tympani, 



a thin, elliptical, semi-transparent and elastic membrane, four and 

 a half lines in its vertical diameter, forming a partition between the 

 cavity of the tympanum and the external auditory meatus, with the 

 inferior wall of which it describes an angle of about 45. Its exter- 

 nal surface looks also obliquely outwards and downwards into the 



18 



