162 



EXPERIMENTAL PHYSIOLOGY. 



LESSON XXXI. 



THE GRAPHIC METHOD MOIST CHAMBER 

 SINGLE CONTRACTION WORK DONE. 



1. Recording Apparatus. For this purpose a revolving cylinder 

 v r ered with smoked glazed paper, or other moving surface is re- 



1. 



covered 



quired. The velocity of the moving surface is usually determined 

 by recording simultaneously the vibrations of a tuning-fork, 



of known rate of vi- 

 bration, or an electro- 

 magnetic time-marker. 

 It does not matter par- 

 ticularly what form 

 of recording drum is 

 used, provided it moves 

 smoothly and evenly, 

 and is capable of being 

 made to move at dif- 

 ferent rates as required. 

 In Hawksley's form 

 this is accomplished by 

 placing the drum on 

 different axles, moving 

 at different velocities. 

 In Ludwig's form (Fig. 

 60), this is done by 

 moving a small wheel, 

 n, on a large brass 

 disc, D. Where a num- 

 ber of men have to be 



Fig. 60. Ludwig's revolving cylinder, R, moved taught at once, one 

 by the_clock-work in the box, A, and regulated mu * t have recou ; se to 



by a Foucault's regulator on the top 

 box. The disc, D, moved by the clock- 



of the 



work, an arrangement of 



presses ui>on the wheel, n, which can be shafting, moved, say 

 raised or lowered by the screw, L, thus alter- by a water-motor or 

 ing the position of n on D, so as to cause the turbine and from whiVh 

 cylinder to rotate at different rates. The >me ^nd 



cylinder itself can be raised by the handle, t. se T eral drums can be 

 On the left aide of the figure is a mercurial driven by cords. Or 

 manometer. one may use a small 



gas engine as the mo- 

 tive power, and cords passing over pulleys to move the drums. 



