292 ANIMAL MECHANISM. 



exist on the opposite side, within the barrel : the use of 

 the eustachian tube (so called from Eustachias, the 

 discoverer) is to admit it. Nothing, therefore, is more com- 

 pletely an imitation of the tympanum of the ear, than the 

 martial drum, which has a little hole in the side, equiva- 

 lent to this we are describing, descending to the mouth, 

 the nearest point from which atmospheric air could be 

 taken, without disarranging or disturbing the functions 

 of vital organs. By closing the sounding hole of the 

 drum, the music is less audible sounding, when the 

 air inside becomes rarefied, like music in a well. The 

 reason is, the equal balance of air is destroyed : such 

 is the object and office of the eustachian tube. Some- 

 times, in violent sneezing, or sudden cough, thepatulous 

 mouths get stopped for an instant with saliva; and many 

 readers are probably familiar with the sensation of fulness 

 that ensues, giddiness and ringing in the ears, to the 

 annihilation of accurate auricular perceptions, till the 

 cause is removed. In bathing, it is not unusual to get, 

 as it is quaintly called, a bubble in the ear, producing 

 these characteristic symptoms. ( 3 ) 



There are many existing cases of deafness, having 

 their origin in some such cause : the pipe finally inflames, 

 and becomes permanently sealed : a skilful aurist, un- 

 der such circumstances, will adroitly puncture the drum 

 head, with an instrument purposely constructed and 

 relieve the patient, without pain. 



FENESTRA OVALIS. 



Fenestra Ovdlis means an oval window covered by one 

 of the two little drum heads. Beyond this, supposing a 

 person could pass through, he would arrive in the vesti- 



(3) Notwithstanding the fine arguments of medical writers to 

 the contrary, I believe that partially deaf persons hear better when 

 the mouth is open ; instinctively, it may be observed, such indivi- 

 duals listen with an open mouth. The pulsations of sound thus 

 enter the tympanum and set the fenestra ovalis vibrating, but 

 very much less forcibly than through the external opening, in its 

 healthful condition. 



