106 COMPARATIVE ELECTRO-PHYSIOLOGY 



Under over-stimulation, the stages D and E are reached, 

 characterised by diminished amplitude of response, or actual 

 reversal into positive. There are thus two conditions under 

 which we obtain abnormal positive responses. One of these 

 is that of sub-tonicity, and the other, the reversal due to 

 fatigue. 



There is, again, no tissue which is exclusively characterised 

 by any specific type of response. All these staircase, 

 uniform, and fatigue will occur in muscle, nerve, plant, 

 and even inorganic matter, under certain definite and ap- 

 propriate conditions. In a future chapter, we shall study in 

 detail the characteristic molecular curve, from which light 

 will be thrown on the internal molecular condition of the 

 tissue, and the influence of that condition on response. 



