442 



SCIENCE PROGRESS. 



forth in great detail in Prof. Biedermann's work, but two 

 extensions of the inquiry by English physiologists are too 

 recent to be included and may be referred to here. The 

 first is that made by Waller. 1 It consisted in recording 

 photographically the galvanometric deflection produced by 

 the aggregate of all the changes when the nerve is stimu- 

 lated for a short period by a rapid series of excitations. 

 The experiment is repeated over and over again at regular 

 intervals and the resulting deflection caused by each series 

 of stimuli thus occurs again and again and these can be 

 photographed one after another upon a slowly moving 

 sensitive plate. The results are valuable inasmuch as they 

 are records admitting of comparison. They demonstrate 

 that nerve is practically incapable of fatigue and show the 

 extent to which both its functional capacity and its excita- 

 bility are modified by changes in its environment. The in- 

 fluence of anaesthetic vapours of carbonic acid and carbonic 

 oxide gases, of saline and acid reagents, etc., have been 

 studied in this way ; and the method undoubtedly opens up 

 the possibility of determining in a more precise manner 

 than heretofore the important question as to the mode in 

 which chemical and pharmacological substances affect the 

 nervous system. 



The second method 2 is that employed by the present 

 writer in conjunction with G. J. Burch. This consists in a 

 special adaptation of the plan of research used by Burdon 

 Sanderson in studying the electromotive phenomena of 

 muscle. 



It will be sufficient here to mention that it is dependent 

 upon the employment of a special instrument, the capillary 

 electrometer. This is particularly sensitive to rapid elec- 

 trical change, and indicates the presence of such changes 

 by a movement in the surface or meniscus of a fine mer- 

 curial column. The movement can be recorded by project- 



1 Waller : "Observations upon Isolated Nerve". — Phil. Trans., 1896. 

 Croonian Lecture. 



2 Gotch and Burch : "The Electrical Response of Nerve to a Single 

 Stimulus investigated with the Capillary Electrometer". — Proc. Royal 

 Society, London, cxiii., p. 300, 1898. 



