1 1 62 THE EAR. 



tightly into the external auditory meatus. It was then found that, after 

 closing the nostrils, the first stage of deglutition caused the fluid to rise slightly 

 in the manometer. The rise was quickly followed by a considerable fall during 

 the second portion of the act, and the fluid remained at the level to which it had 

 fallen until deglutition with the nostrils opened was again performed. This 

 would appear to indicate that, when the nostrils were closed, the air in the 

 pharyngeal cavity communicated with that in the tympanic cavity at the 

 beginning of swallowing, thus causing a rise of pressure. Further, that in the 

 later portion of the time of swallowing, the tube still seemed to be open, so as 

 to allow of some of the air being sucked out of the tympanic cavity, causing 

 a fall of pressure. The tube then was closed and remained closed until the 

 next process of deglutition. 



With the same instrument, Politzer found that in many individuals slight 

 fluctuations occurred, synchronous with expiration and 

 inspiration, even when these acts were quietly performed, 

 showing that the tube, in some persons, may be slightly 

 open, even when the muscles of deglutition are not in 

 action. He also states that air passes more readily from 

 422 E ^ e ty m P anum to tne pharyngeal cavity than in the reverse 



Dieter' Politzer U ~ direction, probably owing to the suction- like action of the 



larger cavity. 



It has also been observed that in a case of paralysis of all the muscles 

 attached to the cartilaginous portion of the tube, a falling inwards of the 

 membrana tympani occurred, from absorption of air in the tympanic cavity 

 and consequent diminished pressure, thus showing that the muscles are necessary 

 for the passage of air into the tympanum (Gray). 



We may conclude that, during rest, the condition of the Eustachian 

 tube varies from a position of slight opening to gentle closure. When 

 swallowing occurs there is a firm closure of the tube, caused by the 

 upward pressure of the levator palati. This is quickly followed by the 

 tube becoming widely opened, chiefly by the action of the tensor palati. 



AUDITORY EEFLEXES. 



As has already been noticed (p. 1157), Pollak 1 has observed the 

 peculiar fact, that when a sound is led to one ear, a reflex contraction of 

 the tensor tympani of the opposite ear occurs ; high notes produce this 

 reflex better than low ones. 



Lucae 2 maintains that a reflex contraction of the stapedius occurs 

 simultaneously with voluntary contraction of the facial muscles, particu- 

 larly the orbicularis palpebrarum. This produces a deep humming 

 noise in the ear, and a relaxation of the tympanic membrane. Accord- 

 ing to Politzer, 3 during this contraction the perception of the middle 

 and the deeper notes of the tuning-fork is destroyed. The present 

 writers, however, cannot corroborate this latter statement. 



Politzer 4 and Helmholtz 5 have observed that during yawning a 

 reflex contraction of the tensor tympani occurs, causing slight temporary 

 deafness. 



A peculiar aural reflex has been described by Gray. 6 If a watch or 



1 Med. Jahrb., Wien, 1886. 2 Arch. f. Ohrenh., Bel. ix. S. 184. 



3 " Diseases of the Ear," 1894, p. 69. 



4 Arch./. Ohrenh., Bd. iv. S. 23. 



5 Arch.f. d. ges. PhysioL, Bonn, 1868, Bd. i. S. 1. 



6 Proc. Roy. Soc. Edin., 1897, vol. xxi. p. 443. 



