FUNCTIONS OF THE CHOKDA TYMPANI. 155 



tensor tympani sliould produce an increased susceptibility 

 of the ear to ordinaiy sonorous vibrations. Contrary to 

 what might be supposed, it is pretty certain that the mem- 

 brane of the tympanum vibrates most intensely when it is 

 relaxed, the vibration being much less when it is rendered 

 tense by the action of the large muscle of the malleus. This 

 view is accepted by Muller, who repeated and extended the 

 experiments of Savart. Muller states that this is a physical 

 law with regard to membranes of the extent of the tympa- 

 num. 1 It is farther carried out by certain cases of paralysis 

 of the facial in the human subject, which present, among 

 other symptoms, a painful sensibility of the ear to powerful 

 impressions of sound. One of the earliest observed and 

 most remarkable of these is the case of Prof. Roux, of 

 Paris, who suffered from a temporary facial paralysis, and 

 who noted that " the membrane of the tympanum was pain- 

 fully sensible even to slight noises." a This symptom has 

 often been noted in facial palsy. 3 



The fourth branch, the chorda tympani, is so important 

 that it demands special consideration. The fifth branch is 

 given off opposite to the origin of the chorda tympani and 

 passes to the pneumogastric, to which nerve it probably sup- 

 plies motor filaments. We have already seen, in studying 

 the properties of the roots of the facial, that in this branch, 

 sensory filaments pass from the pneumogastric and consti- 

 tute a part of the sensory connections of the facial. 4 



Functions of the Chorda Tympani. This branch passes 

 between the bones of the ear and through the tympanic cav- 

 ity to the lingual branch of the inferior maxillary division 

 of the fifth, which it joins at an acute angle, between the 

 pterygoid muscles. It has been a question whether this 



1 MI-LLER, Elements of Physiology, London, 1843, vol. ii., p. 1256. 

 8 BELL, The Nervous System, London, 1844, p. 329. 



3 BERNARD, Lerons sur la physiologic et la pathologic du systeme ncrvevx, Paris, 

 1858, tome ii., p. 114. 



4 See page 153. 



