EXCITATION OF NERVE AND MUSCLE BY GALVANIC CURRENT 53 



produced not only at the make and break, but also during the passage, 

 and for a short time after the cessation of a strong constant current. 



2. An instructive variation of this experiment is to dissect out the 

 rectus abdominis muscles of a curarised frog, and place the non-polaris- 

 able electrodes one in con- 

 tact with the anterior, the 

 other with the posterior end 

 of the flat muscular mass 

 (Fig. 46). The muscles are 

 divided into several seg- 

 ments by tendinous septa, 

 and it will be seen that 

 during the passage of the 

 constant current each of 

 these segments has the 

 part directed towards the 

 kathode in a condition of 

 contraction, and the part 

 directed towards the anode 

 in a condition of relaxa- 

 tion. 



3. The effect of the poles 

 of a constant current upon 



cardiac muscle can be exhibited on the frog's heart. The frog is killed 

 by destroying the brain, and the heart is exposed in situ. Using non- 

 polarisable electrodes and the whole current of a Daniell cell with a 



FIG. 45. Polar effects of constant current 

 upon curarised sartorius. 



FIG. 46. Polar stimulation of rectus abdominis. m, Muscle curarised and 

 stretched between two pieces of cork. 



mercury key and a commutator in the circuit, place one electrode in 

 the mouth or on any other part of the body of the frog, and connect the 

 other, by means of a short piece of cotton-wool wetted with Ringer's 

 solution and drawn to a point, with the heart, so as to touch it near 



