( 48 ) 



For a plain muscle whose fibres are parallel as in the M. sartorius 

 of Rana, the above method is a rather tit one, though not in all 

 respects. For the shortening of the muscle is accompanied by a 

 thickening, in consequence of which the distance between muscle 

 and glass-tear is somewhat altered. This is not of much importance 

 for the thin M. sartorius, but if the experiment is made with muscles 

 like M. gastrocnemius, this difference becomes more considerable, so 

 that it ought to be taken into account. Besides the peculiar rounding 

 of the surface of the muscle may somewhat alter the place of tapping, 

 and in the end the glass-tear sometimes slightly sticks to the muscle, 

 when we are tapping with a small load on the longer beam of the lever. 



To meet these and similar drawbacks the following alterations 

 were made. Between muscle and tapping glass-tear is inserted a thin 

 glass plate, which intercepts the taps and transfers them to the 

 muscle. In these circumstances the angle of reflection resp. the 

 number of collisions depends on: 



1. the cohesion, elasticity, plasticity of the tapping glass-tear; 



2. the cohesion, elasticity, plasticity of the inserted glass plate; 



3. the cohesion, elasticity, plasticity of the object to be examined. 

 Sub 1 and 2 remaining constant, only sub 3 is variable. 



In order to come to a determination, the following technical 

 precautions ought to be taken into consideration. The glass plate, a 

 covering glass, is hanging, slightly movable, on a couple of rather 

 stiff horse-hairs. Now the muscle presses this glass plate against an 

 immovable metal fork, so that the glass plate can only make move- 

 ments in one direction, viz. in the direction of the muscle, as soon 

 as the glass plate is hit by the tapping glass-tear. At every touch of 

 the covering glass the glass globule produces a clearly audible tap. 

 The number of taps is easy to count and is a pretty accurate measure 

 for the number of real movements of the glass, without agreeing 

 with it in number. In proportion as the covering glass is pressed 

 more against the fork by a harder mass of muscles, the oscillations 

 of the little lever will retain a longer and wider amplitude and will 

 also occur more frequently. 



The height of falling is of great importance for the effect that is 

 to be reached, in the first place with respect to the number and 

 amplitude of the oscillations. 



When at different heights of falling the number of corresponding 

 audible taps is counted for the same muscle, the latter may be 

 represented by a curve, in which the ordinate renders the number 

 of audible taps and the abscis the height of falling in degrees. The 

 curve thus got shows a peculiar course. 



