90 INNERVATION. [CHAP. XVIII. 



Savart showed by the following simple experiment that the latter 

 cause was obviously the most effective. He prepared a second conical 

 tube open at both ends, and having placed the narrow end of this 

 tube very near the paper on the former one, but not in contact with 

 it, he found that vibrations were excited on the paper by bringing the 

 vibrating glass near to the wide end of the second tube, but that 

 these vibrations were not nearly so extensive as when the glass was 

 brought near to the wide extremity of the tube with which the 

 paper was connected. 



Hence Savart inferred that the external ear and meatus were parts 

 adapted to enter into vibrations in unison with those of the air, 

 or of any liquid or solid vibrating medium which might be brought 

 in contact with the auricle \ and he suggested that the latter part, 

 in the human subject, by the variety of direction and inclination of 

 its surfaces, could always present to the air a certain number of 

 parts whose direction is at right angles with that of the molecular 

 movement of that fluid, and therefore in the most favourable cir- 

 cumstances for entering into vibration with it. 



We get a general notion of the value of the external part of 

 the auditory apparatus in collecting and directing the sonorous 

 undulations, from the assistance often derived in hearing by placing 

 the hand behind the external ear, so as to increase its concavity ; 

 and by the dulness of hearing, which it is said follows the loss 

 of the auricle. Kerner states that the loss of the auricle is fol- 

 lowed by the greatest dulness of hearing in those animals in which 

 the osseous meatus is wanting. In a cat from which the right ear 

 was cut away close to the skull, after the wound had healed without 

 any stoppage of the meatus, there was a remarkable disposition 

 always to keep the head turned so as to be ready to receive sounds 

 with the left ear, and this continued even after the left tympanic 

 membrane was perforated, the right remaining whole ; and when 

 the left ear was stopped, (although the right tympanic membrane 

 was sound, and the only injury on that side was the removal of the 

 auricle) a total deafness was manifested except to the loudest and 

 clearest sounds. 



The Tympanum and its Contents. We have already stated that 

 Savart had demonstrated experimentally upon the membrana tym- 

 pani itself, that that membrane can be thrown into vibrations by 

 undulations of the air excited by a sonorous body. In a second 

 experiment, the cavity of the tympanum was opened, so as to ex- 

 pose the ossicles of the ear and their muscles ; and it was observed 

 that when the internus mallei muscle acted and rendered the mem- 



