162 SPECIAL SENSES. 



pressure of air is equalized, and the ear returns to its normal 

 condition. The above is the experiment indicated by Toyn- 

 bee, as a demonstration of the action of the pharyngeal mus- 

 cles ; 1 but this observer was in error in supposing that the 

 Eustachian tube is perfectly closed in the quiescent state; 

 for there probably always remains a narrow chink admitting 

 the passage of a small quantity of air ; at least, this is the 

 opinion of most modern writers upon the physiology of the 

 ear, particularly Lucae and Schwartze, who noted an outward 

 movement of the membrana tympani with the inspiratory act, 

 in healthy persons during tranquil respiration. 2 In describ- 

 ing the dilator tubse, Riidinger states that he has confirmed 

 the observations of Troltsch and Mayer, who have shown that 

 there is a direct transition of this muscle into the tensor tym- 

 pani. 3 The nerves animating the dilator tubse come from the 

 pneumogastric and are derived from the spinal accessory. 4 



A smooth mucous membrane forms a continuous lining 

 for the Eustachian tube, the cavity of the tympanum, and 

 the mastoid cells. In all parts, it is closely adherent to the 

 subjacent tissues, and, in the cavity of the tympanum, is very 

 thin. In the cartilaginous portion of the Eustachian tube, 

 there are numerous mucous glands, which are most abundant 

 near the pharyngeal orifice, and gradually diminish in num- 

 ber toward the osseous portion, in which there are no glands. 

 Throughout the tube, the surface of the- mucous membrane 

 is covered with conoidal cells of ciliated epithelium. The 

 membrane of the tympanic cavity is very thin, consisting of 

 little more than epithelium and a layer of connective tissue. 

 It lines the walls of the cavity, the inner surface of the mem- 

 brana tympani, is prolonged into the mastoid cells, and cov- 



1 TOYNBEE, Diseases of the Ear, Philadelphia, 1860. 



2 LUCAE, Ueber die Respirationbewegung des Trommelfells. Archiv fur Oh- 

 renheilkunde, Wurtzburg, 1864, Bd. i., S. 96, et seq. 



SCHWARTZE, Respiratorische Bewegung des Trommelfells. Ibid., S. 139, et seq. 



3 RUDINGER, in STRICKER, Manual of Human and Comparative Histology, 

 The New Sydenham Society, London, 1873, vol. Hi., p. 71. 



4 See vol. iv., Nervous System, p. 207. 



