94 Mr. Francis Gotch [April 28, 



WEEKLY EVENING MEETING, 

 Friday, April 28, 1893. 



Sin James Crichton-Browne, M.D. LL.D. F.R.S. Treasurer and 

 Vice-President, in the Chair. 



Francis Gotch, Esq. M.A. F.E.S. 



The Transmission of a Nervous Impulse. 



The lecturer opened with a short account of the present state of our 

 knowledge as to the anatomical structures of nerve-fibres. 



He then described and repeated the experiments of Helmholtz, 

 made 50 years ago, with the object of ascertaining the rate at which 

 a nervous impulse was conducted along a nerve-fibre. These experi- 

 ments form the basis of our more exact knowledge as to that capacity 

 for transmission which is the peculiar vital function of nerves. 



The essential feature in the process is the power which each in- 

 dividual part of the living nerve-fibre possesses of awakening in 

 response to a sudden change in its physical environment, this property 

 being expressed by the term " excitability " ; in the transmission of 

 the nervous impulse each successive individual part awakens in 

 consequence of the subtle changes present in its aroused neighbours. 

 The awakening thus travels along the nerve as a flame along a fuse. 



The power of transmitting a change, and the power of initiating 

 such change in response to a stimulus, in other words, conduction 

 and excitability, are thus brought into correlation. 



The lecturer then proceeded to demonstrate and describe experi- 

 ments carried out by Mr. J. S. Macdonald and himself, in the 

 Physiological Laboratory of University College, Liverpool, upon 

 this subject, these experiments having been made in order to ascer- 

 tain how far these two properties, (a) of responding to an external 

 stimulus, (b) of transmitting the nerve impulse started by such a 

 stimulus, could be considered as identical. 



In order to ascertain this, an agent was used to modify, on the 

 one hand, the capacity of the nerve to be aroused by physical agencies, 

 and on the other, its power of transmitting an impulse when aroused. 

 The agent employed was a localised alteration in temperature, and 

 experiments were described and demonstrated which showed that 

 whereas cooling to 5° C. tended to block the transmission, such 

 cooling, far from rendering the nerve less responsive to external 

 stimuli, made it more readily affected by the stimulating influence 

 of a large number of physical agencies. Such agencies were shown 

 to be (1) galvanic currents, (2) condenser discharges, (3) mechanical 



