CHAPTER VI 



CONDUCTIVITY 



Contents: Only processes of excitation are conducted, not processes of 

 depression. Conduction of excitation in its two extreme instances. 

 Conduction in undifferentiated pseudopod protoplasm of rhizopoda. 

 Conduction of excitation with decrement of intensity and rapidity. 

 Conduction of excitation in the nerve. Rapidity of conduction of 

 excitation without decrement. Relation between irritability and con- 

 ductivity. Conduction of excitation with decrement of the nerve after 

 artificial depression of irritability by narcosis. Theory of the decre- 

 mentless conduction of the normal nerve. Proof of the validity of 

 the "all or none law" in the meduUated nerve. Theory of the process 

 of the conductivity of excitation. Theory of core model (Kernleiter). 

 Electrochemical theory of conduction based on the properties of semi- 

 permeable surfaces. 



When the response to a stimulus is studied in a living system, 

 whether it be a single cell, a tissue, or a complex organism, the 

 indicator used, either that of movement, current of action, pro- 

 duction of certain substances, the development of light, of heat 

 or the alteration of form, is the result of two distinct processes. 

 The first of these is primary excitation, brought about by the 

 stimulus at a local point, and the second is an extension of the 

 excitation to the surrounding tissue. We are not in a position 

 to experimentally bring about a response to stimulation, in which 

 the primary excitation occurs and not the secondary process, 

 that of conductivity. All living substance contains this property, 

 although to a very different degree, as all living substance pos- 

 sesses irritability, and this presents the condition not only for 

 the taking place of the process of excitation but also that of its 

 conduction. 



If I here speak only specifically of the conduction of excitation 

 instead of the conductivity of response to stimulation this is not 



