EFFECT OF SUCCESSIVE STIMULI UPON MUSCLE 



39 



tion of the finger muscles may be recorded by resting the hand across 

 the myograph plate and tying a thread to the abducted forefinger, 

 the other end of the thread being attached to the short arm of the 

 lever ; this is to be heavily weighted or to be held down by a strong 

 elastic band. On adducting the finger the lever is raised, and a curve 

 is described on the moving drum which bears a close resemblance to 

 an incomplete and somewhat irregular tetanus produced by ten or 

 twelve stimulations per second. 



It must not be concluded that this represents the rate of the 

 successive individual contractions which fuse to form the voluntary 



FIG. 38. Experiment to investigate the genesis of tetanus. a, Flat steel 

 spring marked at intervals with the number of vibrations corresponding 

 to certain lengths of the spring ; b, mercury cup into and out of which a 

 platinum wire attached to the spring dips. 



contractions, for it has been shown by photographic records of the 

 capillary electrometer (see p. 61) that in a voluntary contraction there 

 are not less than fifty electrical changes per second, and this probably 

 also represents the number of mechanical changes which succeed one 

 another in a voluntary contraction. The causation of the waves of 

 ten or twelve per second is not fully understood. 



Another method of obtaining the curve of a voluntary contraction 

 is by the use of a transmission myograph, which consists of two tam- 

 bours connected by india-rubber tubing. The first or receiving 

 tambour (which may be represented by an ordinary Marey's cardio- 



