AXIMAL ELECTRICITY 



567 



to the ventral surface. In Gymnotus the shocks are from tail to head, 

 in Malapterurus from head to tail, the direction depending upon the 

 point of entrance of the nerres to the organ. A giant ganglion cell 

 and its nerve fibre, branching multitudiiiously, supplies the whole of 

 each electric organ in this fish. 



Blaze Currents. After any living tissue has been strongly tetanized 

 for a short space of time, a ' ; blaze " current follows in the same 

 direction as the tetanizing current. This is a sign of life; dead 

 tissue does not give it. Seeds have been tested by this means, and 

 their germinating power thus demonstrated. 



Electrotherapy. Eleatrlcity is largely employed in the treatment 

 of disease. It may act by producing either chemical or thermal 

 effects. In the first case, the galvanic electric current is used, since 

 it causes a steady migration of positive ions to the negative pole, and 

 of negative ions to the positive pole. It may be employed thera- 

 peutically for three purposes: (1) To produce an alteration in the ionic 



Fia. 308. NERVOUS STRUCTURES STIPPLED, STRIATED STRUCTURES INDICATED BY 

 LINES. (Redrawn from Dahlgren and Kepner.) 



a, Diagram of muscle fibre; &, of electroplax of Raja baltf ; c, diagram of electroplax 



of Raja Iceois. 



content of a region, as is probably the case when used for promoting 

 the absorption of fluid effusion?. (2) To cause a formation and 

 accumulation of new chemical bodies at the poles. Such bodies 

 may have a caustic action, and be used for the destruction of hair 

 follicles (superfluous hairs), nsevi, etc. (3) By means of the current 

 to introduce curative ions through the skin the " ionic method of 

 medication." 



The faradic current cannot be used for the above purposes, since the 

 current is frequently made and broken. The ions then migrate in 

 sudden movements or jerks, and act as a stimulus to excitable tissue, 

 such as muscle. The faradic current is of great value in the treat- 

 ment of paralysis. 



If an interrupted current be made to oscillate with extreme 

 rapidity across the body, the ions do not have sufficient time to act as a 

 stimulus, and remain more or less stationary. Under these conditions, 

 a powerful current (3 amperes), six times stronger than a current 



