THE MUSCLE-NOTE. 43 



commencement of the tetanic condition, or during each 

 distinct pulsation, a portion of this force occurs in the 

 form of mechanical work. 



There is yet another fact which shows that internal 

 motion must proceed within the muscle when con- 

 tracted in tetanus, notwithstanding the quiescent con- 

 dition in which externally it apparently is. A muscle 

 when in this condition produces a sound or note. On 

 placing an ear-trumpet on any muscle, for instance, on 

 that of the upper arm, and then causing the muscle to 

 contract, a deep buzzing noise is audible. This may 

 also be loudly and distinctly heard on stopping the 

 outer ear-passages with waxen plugs, and then contract- 

 ing the muscles of the face ; or by inserting the Little 

 ringer firmly in the outer ear-passage and then contract- 

 ing the muscles of the arm. In the latter case the 

 bones of the arm conduct the muscle-note to the ear. 

 This muscular note clearly shows that vibrations must 

 occur within the muscle, however apparently unchanged 

 the form of the latter may be. We found that teta- 

 nus thus apparently constant is induced by distinct 

 irritants applied in quick succession. Helmholtz has 

 shown that each of these irritations really corresponds 

 with a vibration ; for, if the number of the distinct 

 irritations is altered, the muscle-note is also changed, 

 the height of the muscle-note always corresponding 

 exactly with the number of irritants applied. Though, 

 therefore, no alteration in form can be perceived in the 

 tetanised muscle, this can only be due to the fact that 

 movements which occur among the particles within the 

 muscle effect the note, though the external form re- 

 mains unchanged. A somewhat similar phenomenon 

 is observable in rods when caused to vibrate longitu- 



