IT CHANGE OF FORM IX MUSCLE DURING ACTIVITY 135 



Returning to the consideration of steady, complete tetanus, 

 we have next to ask whether the excited state of the muscle is 

 really continuous, as it appears from the curve to be, or if, not- 

 withstanding appearances, discontinuous alterations of condition 

 can be demonstrated, which follow in the usual course, but are 

 not expressed in corresponding form-changes. It is conceivable 

 that the contractile elements of the muscle may be thrown into 

 new equilibrium, and maintained at the same as long as excita- 

 tion continues, by the stimuli which follow at a given rapidity ; 

 or we may assume not only the excitation, but also muscular 

 contraction itself, to be a discontinuous process, in which a 

 vibratory movement of the smallest particles of the muscle-fibres 

 corresponds with each impact of stimulation. Experimentally, 

 there is strong reason for supposing that electrical tetanus is 

 really discontinuous, notwithstanding its apparent continuity. If 

 we touch a muscle, or, better, a whole limb, that is in rigid 

 tetanus, a vibration is easily felt which can be expressed object- 

 ively by delicate graphic methods, as well as subjectively in the 

 so-called muscle-sound or muscle-tone, and by the tremor of the 

 shiny surface of the muscle in tetanus, as Briicke (28) observed 

 through the skin of a man's arm when suitably illuminated. 

 Helmholtz obtained an objective demonstration of the vibrations 

 of tetanised muscle by fixing a watch-spring or paper flag on to 

 an elastic board, attached to the muscle (29). The springs 

 vibrate consonantly when their own vibration period coincides 

 with that of the tetanised muscle. And a thread attached to the 

 tendon of such a muscle, and stretched tensely, falls, as Engel- 

 mann (22) showed, into longitudinal vibrations, which can com- 

 municate perceptible impacts to a light recording lever. Since, 

 further, rapid vibrations (e.g. of tuning-forks) may be conveyed . 

 through air-capsules with perfect accuracy, the quick tremor of 

 the tetanised muscle is able, without any noticeable change in its 

 length, to set the lever vibrating at comparatively large ampli- 

 tudes according to the above method, cf. Marey's pince myo- 

 graphique (Kronecker and Hall, 3 ; v. Limbeck, .30). 



These facts are even more interesting in reference to the 

 much-disputed question whether the natural, voluntary or reflex, 

 persistent contraction of striated muscle is produced by a rhyth- 

 mically self-repeating impulse, as in artificial tetanus. 



Wollaston (1810) and Ermann (1812) attempted to apply 



