COMPARATIVE ELECTRO-PHYSIOLOGY 



CHAPTER I 



THE MOLECULAR RESPONSIVENESS OF MATTER 



Response to stimulus by change of form Permeability variation Variation of 

 solubility Method of resistivity variation : (a) positive variation ; (b) 

 negative variation Sign of response changed under different molecular 

 modifications Response of vegetable tissue by variation of electrical re- 

 sistance Response by electro-motive variation in inorganic substances 

 The method of block Positive and negative responses Similar responses in 

 living tissues Effects of fatigue, stimulants, and poisons on inorganic and 

 organic responses Method of relative depression, or negative variation, so 

 called. 



IN studying the properties of living tissues, we find one of 

 their most important characteristics is found in the fact 

 that they exhibit the state of excitation under the impact of 

 stimulus. On the cessation of stimulus, again, the excited 

 tissue returns to its original condition. The excitatory change 

 thus undergone is fundamentally due to the derangement, or 

 upset, of the molecules of the living tissue from their normal 

 equilibrium, recovery being brought about by their restoration 

 to that state. The excitatory condition is sometimes shown 

 by change of form, as in the case 

 of the shortened length of excited 

 muscle (fig. i). This might be 

 compared with the shortening of 



..... . . , FIG. I. Series of Contractile 



stretched india-rubber under ther- Responses in Muscle 



mal stimulus (fig. 2). 



Now it is clear that the molecular change consequent 

 on excitation must occasion various concomitant physical 



B 



