1917] on The Organs of Hearing in Relation to War 93 



the internal ear can be completely disorganised by a missile snch as a 

 bullet passing through the head near the internal ear without actually 

 touching it. This event is also observed in the retina of the eye. 

 It is known as " commotion " or concussion, and when affecting the 

 hearing produces what the French term " surdite a distcmce." [The 

 damage to the structures of the internal ear by direct violence was 

 illustrated by micro-photographs of sections made by Dr. J. Fraser, 

 of Edinburgh. Kadiograms were thrown on the screen showing the 

 appearance of a normal temporal bone, a temporal bone (petrous 

 portion) rendered indistinct by the presence of the products of 

 contusion and inflammation, and another with a fracture of the skull 

 passing through the internal ear.] 



Second. — The force of the compression of the air., such as is 

 induced by the explosion of a shell, frequently causes deafness by 

 driving in the tympanic membrane and, with it, the small bones of 

 the ear so as to induce a violent concussion of the internal ear. This 

 appears to act most severely in those in whom there has been previous 

 disease of the middle ear itself, or of the Eustachian tube and nasal 

 passages. (Such diseases unless cured would exclude the candidate 

 from the Flying Corps.) The explosion may at the same time rupture 

 the tympanic membrane, and in this case some of its force is spent 

 before it reaches the inner ear. It is found that cases of deafness 

 due to concussion of the labyrinth are more likely to recover if there 

 is concomitant rupture of the tympanic membrane. [The physical 

 conditions accounting for this were illustrated by an experiment 

 devised for the purpose. A light wooden hoop covered with a fairly 

 resistant paper w^as hung by a hinge over the end of a drain-pipe. 

 A revolver with blank cartridge was fired into the other end of the 

 pipe and the concussion forced the hoop upwards on its hinge with 

 great violence. The firm paper was replaced by a very thin one, and 

 when the revolver was again discharged the paper gave way, W'hile 

 the movement of the hoop was exceedingly slight.] 



Third. — The mere loudness of the noises^ either one definite 

 exposure or a continuation of such, may produce deafness by over- 

 stimulation of the auditory fibres (or nerve-centres). Castex has 

 shown the damaging effect of continued exposure to the sound of 

 gunfire on guinea-pigs. Yoshii, Siebenmann and Wittmaack have 

 exposed guinea-pigs to continuous sounds of different pitch. Patches 

 of degeneration of the auditory cells were found in the cochlea, nearer 

 its apex in those exposed to low-pitched tones, and nearer the base in 

 those exposed to the higher-pitched ones. [The lecturer expressed 

 regret that we had to depend on foreign experimenters for such 

 important investigations. With us research was very poorly paid, 

 either in money or in social distinction, and the teacher or original 

 investigator had usually to support himself by the practice of medicine. 

 Furthermore, we were hampered by unreasonable restrictions in the 

 pursuit of truth in physiology by experiments on lower animals. 



