CONDUCTIVITY IN MUSCLE 477 



Recording the Effects of a Single Induction Shock. With a muscle-nerve 

 preparation arranged in either of the above ways, on closing or opening the 

 key in the primary circuit we obtain and can record a contraction, and if we 

 use the clock-work apparatus revolving rapidly, a curve is traced such as is 

 shown in figure 320. 



Another way of recording the contraction is by use of the pendulum myo- 

 graph, figure 352. Here the swing of the pendulum along a certain arc is 

 substituted for the clock-driven movements of the other apparatus. The 

 pendulum carries a smoked-glass plate upon which the writing lever of a 



FIG. 319. Arrangement of the Apparatus Necessary for Recording Muscle Contrac- 

 tions with a Revolving Cylinder Carrying Smoked Paper. A, Revolving cylinder; B, the 

 frog arranged upon a cork-covered board which is capable of being raised or lowered on the 

 upright, which also can be moved along a solid triangular bar of metal attached to the base 

 of the ^recording apparatus the tendon of the gastrocnemius is attached to the writing 

 lever, properly weighted, by a ligature. The electrodes from the secondary coil pass to the 

 apparatus being, for the sake of convenience, first of all brought to a key, D (Du Bois 

 Reymond's); C, the induction coil; F, the battery (in this figure a bichromate one); E, 

 the key (Morse's) in the primary circuit. 



myograph is made to mark. The opening or breaking shock is sent into the 

 nerve-muscle preparation by the pendulum in its swing opening a key, figure 

 352, C, in the primary circuit. A muscle or its nerve is more irritable to an 

 opening shock than it is to a closing shock of the same strength, because the 

 duration of the former is shorter than that of the latter. 



Conductivity in Muscle. In an ameba or other simple undifferentiated 

 contractile protoplasmic unit a stimulus applied at any point is quickly 

 transmitted throughout the entire mass. Just so is it with differentiated 



