52 



EXPERIMENTAL GENERAL PHYSIOLOGY 



circuit of many turns of fine wire. It will be assumed that th< 

 principle of the inductorium is familiar to the student through hi; 

 previous work in physics. (See Figs. 29 and 30.) 



The inductorium used in the physiological laboratory is providec 

 with a vibrating (Neef) hammer which makes and breaks the curren 

 with each double vibration of the hammer, the vibration bein^ 

 due to the reciprocal action of an electromagnet and a spring. Th< 

 instrument must also be provided with a means for either cutting th< 

 hammer out of the primary circuit or stopping the vibration o 

 the hammer. The secondary coil or induction circuit must be pro 

 vided with a short-circuiting key, either as a part of the inductoriun 

 or as an extra appliance. 



FIG. 32 



FIG. 33 



The kymograph. 



Drum support for use in smoking the kymograph drums 



The secondary coil is movable and may be moved up until it coven 

 the primary coil or moved out along a slide. Some instruments are 

 provided with a long base, permitting the secondary coil to be movec 

 to a considerable distance from the primary coil, while others are 

 provided with a short base and a pivot, allowing the secondary coil 

 to be turned through an angle of 90 degrees after it has been drawn 

 back free from the primary coil. Either arrangement allows one 

 to decrease at will the strength of the induction shocks. 



(c) The Kymograph (Fig. 32). This instrument is the mosl 

 important one in any physiological laboratory, because with its help 

 graphic records of all movements of tissues and organs and of all 

 pressure changes may be made. The kymograph or wave-writer is 



