130 GENERAL PROPERTIES OF LIVING TISSUES 



the deeper tissues ; and the large surface offers a 

 broad path for the current, so that the current lines 

 are not so concentrated as to stimulate painfully 

 the sensory nerves of the cutis. One sponge elec- 

 trode may be made considerably smaller than the 

 other without forfeiting this advantage, while the 

 smaller size makes it easier to localize the stimulus. 



Muscles are best stimulated through their 

 nerves, for two reasons : the nerve responds to 

 a weaker stimulus than the muscle ; and, sec- 

 ondly, it is much easier to secure contraction of 

 the whole muscle by stimulating the nerve than 

 by attempting to pass a current through the 

 muscle directly. The smaller electrode should 

 be placed over the nerve, the larger on some in- 

 different region. The indifferent electrode may 

 be placed over the muscle itself, if it is important 

 that the resistance shall not be increased by the 

 too great separation of the electrodes. 



Duchenne found that certain points were es- 

 pecially favorable for the stimulation of indi- 

 vidual muscles. Eemak discovered that these 

 " motor points " were simply the places at which 

 the nerves entered the muscle. The motor points 

 of the forearm are shown in Figs. 35 and 36. 



Stimulation of Motor Points. Arrange the 

 inductorium for single induction shocks. De- 

 termine by the electrolytic method which pole 



