238 



TISSUE CURRENTS. 



Requirements the same as before, and couple the wires 

 from the electrodes to the terminals of the electrometer. 



The latter is set up on a bracket on the wall of the 

 dark room, and consists of a glass tube drawn to a fine 



FIG. 47. G Galvanometer. L Lamp and scale. H Shunt. C Commutator with 

 leading-in terminals in circuit, with E Non-polarisable electrodes. P Paraffin block 

 supporting a muscle, the nerve of which rests on platinum electrodes S connected 

 to S circuit of inductorium. 



1. Non-polarisable electrode. C China clay point on glass tube S con tain ing- 

 saturate zinc sulphate solution. Z Zinc rod (amalgamated) corked into place. 



2. Diagram of capillary electrometer. C Glass tube with capillary end, con- 

 taining mercury (black), dipping into 1 in 10 sulphuric acid A. E Wires of platinum 

 in the electrometer, attached to "leading- off" electrodes. There is an arrangement 

 for exerting pneumatic pressure on the mercury in C to adjust its position in the 

 capillary. The mercury moves in the direction of the negative pole. The electro- 

 meter is substituted for the galvanometer and shunt in the first arrangement l>y 

 attaching its wires to the commutator C. 



capillary end, in which there is mercury, and which dips 

 into a small trough containing 10 p - c - H>SO 4 . There is a 

 small pool of mercury in the latter also. The terminal wires 

 dip into the mercury in each case. 



