234 



PRACTICAL PHYSIOLOGY. 



[XLV. 



the level of the U- sna P e( l tube. The muscle is placed on the 

 two corresponding kaolin caps. 



3. Shunt. This is an arrangement by which a greater or less 

 proportion of a current can be sent through the galvanometer (fig. 

 158). The brass bars on the upper surface 

 are marked with the numbers -J-, -$, -5-^-5-, 

 indicating the ratio between their resistance 

 and that of the galvanometer, so that when 

 the plug is inserted in the several positions, 

 iV> TW> or TTyW ^ tne wn ole current may be 

 sent through the galvanometer. 



4. Muscle Demarcation-Current (Current 

 of Injury). 



(a.) Arrange the apparatus according to the 

 scheme (fig. 159). 



(b.) Place a shunt between the N.P. elec- 

 FIG. 158.- The Shunt, trodes and the galvanometer. Connect two 

 wires from the electrodes to the binding 

 screws (A, B) of the shunt, and from the same binding screws 

 attach two wires to the galvanometer. Insert a plug (C) between 



FlQ. 159. Arrangement of Apparatus for the Demarcation-Current of Muscle. M. Muscle 

 011 a glass plate, P ; S. Shunt ; <?. Galvanometer ; Mg. Its magnet moved by the 

 milled head, in; L. and So. Lamp and scale. 



A and B, thus short-circuiting the muscle- current. "When work- 

 ing with muscle, keep a plug in the hole opposite -- on the 

 shunt. Arrange the lamp and scale so as to have a good image of 



