208 



PHYSIOLOGY 



CHAP. 



tympanic apparatus, owing to its peculiar form, supplies the chief 

 part of what is theoretically requisite, in order that it may vibrate 

 to the different notes of the scale. Mach himself failed after 

 many fruitless attempts to establish any experimental basis for 

 his theory, and gave it up. In this direction the experiments of 

 Schapringer (1870) seem to be conclusive. He was able to 

 contract his tensor muscle at will and found with a suitable 

 manometer introduced into the auditory passage that the tympanic 

 membrane was displaced inwards each time the muscle con- 

 tracted. But he was unable to detect any evidence of accom- 

 modation to different notes of the scale. 



On the strength of his observations on curarised dogs, Hensen 

 concluded that the tensor contracts at the beginning of every 



auditory impression, more vigor- 



7 4 ously for high than for low tones, 



and that in audition it damped 

 the consonants, and favoured per- 

 ception of the accentuated vowels. 

 This implicitly excludes the 

 theory of any true accommodation. 

 Many aurists, nevertheless, hold 

 that there is some tympanic ac- 

 commodation, on the ground that 

 the ticking of a watch is always 

 perceived at a greater distance 

 when it is gradually removed from 



. . , ., , , ... 1-1 



visible by opening the canai which lies the ear than when it is approached 



within the eminence known as the pyramid. fr . - f Thie li'-mina! rlifPar-annP 



1, rnusc. stapedius ; 2, its tendon, emerging tO It. 1D1S liminal Qllierence 



from the pyramid to be inserted on the neck see ms to US to be explicable as a 



of the stapes; 3, tendon of tensor tympani . " 



cut short ; 4, facial nerve cut across ; 5, its Simple phenomenon of attention 



^N^o^-^L^&X^. rather than as an effect of tym- 



panic accommodation. 



The stapedius muscle (Fig. 80) takes origin in a canal of the 

 pyramid. Its tendon issues from the aperture at the apex of 

 that elevation, and is inserted into the neck of the stapes, close 

 to the articulation of that bone with the lenticular process of the 

 incus. Its motor nerve is a small twig of the facial. If the 

 eyelids are closed energetically a sound is heard, which, in all 

 probability, depends on the associated contraction of the stapedius 

 (Lucae). 



Gottstein and more recently Ostmann stated that in listening 

 a special sensation of tension is perceived in the ear, which they 

 referred to the stapedius, as this muscle comes into play directly 

 we try to perceive weak tones or noises. In fact, according to 

 Politzer, Eysell, and Mach and Kessel the contraction of the 

 stapedius by pulling on the stapes throws it into an oblique 

 position in relation to the fenestra ovalis, by driving the anterior 



FIG. SO. Position of stapedius muscle, made 



