BY DR. MICHAEL FOSTER. 369 



The maximum is not the same with all intensities of stimulus. 



Tlu're is a definite relation of load, muscle, and stimulus, 

 by which the greatest amount of work can be got out of a 

 given muscle. 



CHAPTER XXIII. 

 THE WAVE OF MUSCULAR CONTRACTION. 



06s. I. Place a nerve-muscle preparation in a horizontal 

 position, so that the gastrocnemius rests on some flat surface 

 (e. g., a glass plate) over which it can glide freely ; clamp the 

 femur fragment tight ; by means of a pulley attach the tendon 

 to a lever, etc., with a load of 10 or 15 grammes. Bring over 

 the middle of the muscle the button of a light cardiograph 

 connected with a Marey's tambour (see 'p. 265, fig. 230). If 

 the button is large, attach to its under surface a conical piece 

 of cork or some other material, which can be brought into 

 contact with a small portion of the surface of the muscle. 



Bring the recording point of the tambour lever to mark on 

 the cylinder, a little distance below the other lever. 



Place the nerve on the electrodes of an induction coil. 



While the cylinder (first or second axis) is revolving, and 

 the two levers are describing parallel lines, send induction 

 shocks of various strengths through the electrodes. 



The direct lever will indicate the shortening of the muscle, 

 the tambour lever its thickening. It will be seen that they 

 both take place at about the same time, and that with the 

 various strengths of current the movement of one lever in- 

 creases or decreases with the other. 



06s. II. Poison a frog completely with urari, so as to eli- 

 minate as much as possible the influence of nerves. Dissect 

 out carefully one of the large muscles of the thigh ; for in- 

 stance, the rectus interims major (fig. 278, r. i}. Cut away 

 with it the piece of the pelvis, to which its origin is attached. 

 Leave as much of the tendon of insertion as possible. 



Lay the muscle in a small trough (fig. 280) (one can easily 

 be made of gutta-percha), and place over it, as far apart as 

 possible, two levers. The levers must be so arranged that 

 their points write on the cylinder one below the other in ex- 

 actly the same vertical line. Fix the one end of the muscle 

 by clamping the piece of pelvis, and attach by means of a 

 pulley a load of 5 or 10 grammes to the tendon. 



Bring two pointed electrodes from an induction coil, to one 



