4 H COMPARATIVE ELECTRO-PHYSIOLOGY 



citable or in a sub-tonic condition or fatigued. The pre- 

 sence or absence of chlorophyll is not a determining factor 

 in electrical response. As in the case of mechanical and 

 growth responses, so also in the electrical, continuous stimu- 

 lation gives rise to multiple responses, as its direct or after- 

 effect. The sequence of phases, under the direct action of 

 continuous stimulation, may be( -I- + ) or ( + -H ). 

 Taking into account both the direct and after-effect, the 

 observed results may be classified under three types. In 

 the first type, that of fresh and highly excitable tissues, the 

 formula is ( -f !-). In the second or intermediate type, it 

 is ( + ...) or ( ...). And in the third type we have 

 the formula (+ - ...). 



