GENERAL PHYSIOLOGY. 79 



rheocord. Finally with a weak polarizing current, the 

 stimulus in the region of ascending extrapolar kathe- 

 lectrotonus causes a stronger response than normal. 



The response which the muscle makes must be 

 accepted as a measure of the excitation which 

 it receives from the nerve. But the excitation 

 delivered by the nerve depends upon two factors, its 

 irritability and its conductivity. When the nerve is 

 stimulated in the region of ascending extra or intra- 

 polar kathelectrotonus, its increased irritability is of 

 no avail if there is interposed between that region 

 and the muscle a region of decreased conductivity. 

 With strong polarizing currents the region of the 

 anode is not only decreased in irritability but also in 

 conductivity. 

 Laws of electrotonus. 



I. The passage of a constant current through a nerve in- 

 duces a condition of electrotonus marked by an increased 

 irritability in the region of the kathode (kathelectrotonus^) 

 and a decreased irritability in the region of the anode 

 (anelec trot onus} . 



II. During electrotonus induced by a strong current the con- 

 ductivity is decreased in the region of the anode. Further 

 though not derived from the foregoing experiment "at 

 the instant that the polarizing current is withdrawn the 

 conducting power is suddenly restored in the region of 

 the anode and greatly lessened or lost in the region of 

 the kathode."" Lombard, in American text-book of 

 Physiology. 



