78 



PRACTICAL PHYSIOLOGY 



f-orf 



In this figure the lever for vary- 

 ing the strength of the galvanic 

 current is not shown. 



If such an installation is not 

 available GALVANIC CELLS must be 

 used either singly or in series. So 

 many different kinds are now in 

 use that it is unnecessary to de- 

 scribe them here. Probably the 

 Daniell cell (Fig. 74) is the most 

 suitable for physiological purposes 

 on account of the steadiness of the 

 supply of current and of its uni- 

 form voltage. 



The strength of the current may 

 be varied by inserting into the 

 circuit some form of RHEOCORD, 

 FIG. 74. Diagram of a Daniell such as is shown in Figs. 75, 76, 



f 



Pbncu* pot 



cell seen in section. 



77. 



The ends of the wires are gener- 

 ally provided with some form of ELECTRODES for application to 

 the tissues. These may consist of a couple of pins thrust through 



FIG. 75. Simple form of monochord. 



a piece of cork or vulcanite (Fig. 78), or they may be guarded so 

 as to prevent contact with surrounding tissues by being inserted 



FIG. 76. To illustrate the principle of the monochord. 



through a piece of vulcanite [with a notch over the ends of the 

 wires (Fig. 78). 



