PRACTICAL PHYSIOLOGY 



slight effect, the direction and the amount of which 

 should be noticed. Next close the battery circuit, 

 leaving the short-circuiting key open. Part of the 

 battery current is now sent through the electrodes 

 and electrometer in a particular direction (which 

 can be reversed by the commutator), and there is 

 a corresponding movement of the mercury. Note 



Sulphuric acid __ 



Meniscus of 

 mercury 



Tube for trans- 

 mitting pres- 

 sure to mercury 



Mercury passing 

 into capillary 



Dilute sulphuric 

 acid . 



Mercury . 



. .Non-polarisable 

 electrodes. 



FIG. 38. ARRANGEMENT FOR EXAMINING MUSCLE CURRENT BY CAPILLARY ELECTRO- 

 METER. A, DIAGRAM OF ELECTROMETER; B, THE CAPILLARY AS SEEN WITH THE 

 MICROSCOPE. 



the direction of this movement, and by following 

 out the wires from the battery determine with which 

 part of the electrometer the anode and kathode 

 are respectively connected. By means of the 

 rheochord and commutator a definite proportion 

 of the battery current can be sent in either direc- 

 tion through the electrodes i.e., through any 

 preparation with which they may be connected. 



