184 PHYSIOLOGICAL PHYSICS. [Chap. xvm. 



Given the revolving cylinder, very many simple 

 arrangements may be made for the registration of 

 various phenomena. Thus the speed of propagation 

 of the wave of muscular contraction may be very easily 

 measured with the aid of two simple levers. A frog's 

 muscle is laid on a support, one end being tightly 

 clamped by a small forceps, and the other end being 

 attached to a weight by a cord passing over a pulley. 

 One lever is laid across the muscle at one end, and 

 another across the other end. Both levers are caused 

 to project on to the surface of a revolving cylinder 

 placed vertically, the levers being so arranged that the 

 point of the second touches the cylinder directly below 

 the point of the first. The muscle is then stimulated 

 at one end. The wave of contraction, passing through 

 the muscle, lifts the first lever, which writes its curve 

 on the cylinder, and immediately afterwards lifts the 

 second lever, which also writes its curve. Thus two 

 curves are obtained, one a little in advance of the other, 

 and the difference between the two measures the time 

 it took the wave of contraction to pass from one end 

 of the muscle to the other. A chronographic tracing 

 on the same cylinder will indicate the absolute value 

 of this time. 



CHAPTER XVIII. 



THE TRANSMISSION OF MOVEMENT. 



A DEVICE of Marey's, called the tambour or drum, 

 brings within the region of graphic registration many 

 phenomena which it might be impossible to register 

 without it. 



The tambour consists (Fig. 91) of a shallow 

 metallic capsule a, provided with a side tube f. The 

 capsule is closed above by a delicate caoutchouc 



