202 PHYSIOLOGY CHAP. 



destruction or perforation of the fenestra rotunda, and after 

 section of the tendons of the malleus and stapes muscles. 



Microscopical observations on the oscillations of the tympanic 

 apparatus were subsequently repeated by Burnett (1872), Politzer 

 (1873), and Mach and Kessel (1874). By means of the strobo- 

 scopic method, the two latter brought out certain important 

 particulars, as for instance that the fenestra rotunda bulges out- 

 wards when the plate of the stapes dips in towards the vesti- 

 bulum. When very high tones are employed, the excursions of 

 the ossicles become too small to be visible. 



Mach and Kessel further observed the movements of the 

 tympanic apparatus in the living animal, after gilding the mem- 

 brana tympani (1872). Berthold almost simultaneously made 

 similar observations upon living human subjects by the mano- 

 nietric flame method, using the external auditory meatus as a gas- 

 chamber. On applying the tuning - fork to the cranium he 

 obtained good vibrations of the flames in the swinging mirror. 

 Nagel and Sarnojloff (1898) confirmed these results. They also 

 carried out the same experiment on the head of an animal, using 

 the tympanic cavity as a gas-chamber. Vibrations of the flames 

 were obtained not only on conveying tones or sounds of ordinary 

 intensity to the auditory meatus, but also in speaking or con- 

 versing under the breath, which proves the exquisite mechanical 

 sensibility of the tympanic apparatus. 



In comparison with these results obtained by admirable experi- 

 mental methods some more recent experiments carried out by 

 Nuvoli (1907) on the human temporal bone are of less value, but 

 as they present certain new details they deserve a brief description. 

 After opening the roof of the tympanum without injuring the 

 ossicles and their ligaments, he cut the tendon of the tensor 

 tympani, attached to it a thread 30 cm. in length, and fixed the 

 other end of the thread to the centre of the membrane of a 

 filter-shaped stethoscope, connected by two rubber tubes with the 

 observer's ears. On bringing a watch near the external auditory 

 meatus of the anatomical preparation, and lightly stretching the 

 thread so that the tension of the tympanic membrane is some- 

 what increased, the observer plainly hears the ticking of the 

 watch. The same result is obtained if, instead of tying the 

 thread which connects the tympanic apparatus with the binaural 

 stethoscope to the tendon of the malleus muscle, it is attached 

 to the tip of the long process of the incus, after removing the 

 stapes and resecting the portion of the inner wall of the cavity, 

 above the fenestra ovalis. The ticking is also distinctly (though 

 feebly) perceptible if the thread is attached to the centre of 

 the stapes, after dividing the petrous bone so as to open up the 

 cavity of the vestibule widely. These three experiments give 

 no positive results if the tympanic membrane has been put out 



