THE GRAPHIC METHOD 85 



two beats in the minute, but such a record is 

 quite accurate enough for most purposes. The 

 use of a stop-watch marking fifths of. seconds 

 would add nothing to the value of the count, 

 for the error introduced by numberless causes 

 that slightly modify the heart-beat from minute 

 to minute is greater than the error introduced by 

 using an ordinary watch instead of a stop-watch. 

 The correction of errors that are too small to 

 alter essentially the value of the method for 

 the purpose to which it is applied is usually 

 wasteful. 



With these points in mind, smoke a drum. 

 Arrange the inductorium with simple key for 

 maximal break induction currents. Prepare a 

 gastrocnemius muscle, fasten it in the muscle 

 clamp, tie a fine copper wire around the tendo 

 Achillis, wrap the wire about the hook on the 

 muscle lever, and fasten the end in the binding 

 post of the muscle lever (Fig. 21). Connect 

 the secondary coil with the posts on the muscle 

 clamp and muscle lever respectively. Weight 

 the muscle with ten grams. Arrange the lever 

 to write on the drum. Kecord single contrac- 

 tions with various speeds. 



Note that the muscle writes its contraction 

 in the form of a curve, the ordinates of which 

 measure the height to which the load is lifted. 



