ANIMAL ELECTRICITY. LECTURE I. I9 



tioiis, effected or not effected, by all kinds of chemical 

 and physical interference. 



But this very regularity of response has a suspi- 

 ciously non-physiological appearance. The first thing 

 to do is to make sure whether or no it is physiological, 

 and the first step to take is to test it by anaesthetic 

 vapours. The best and most expeditious anaesthetic 

 to employ for this purpose is ether (diethyl oxide). 



Experivient. — The nerve resting upon two pairs 

 of unpolarisable electrodes, one pair for the exciting- 

 current, the other serving to lead off the current of 

 Injury and Its negative variation to the galvanometer 

 (as shown In figs. 5 and 10), is enclosed in a glass 

 chamber into which air saturated with ether vapour 

 can be blown. The negative variation having been 

 provoked once or twice by completing the exciting 

 circuit, and having been found to be sufficiently large 

 and sufficiently regular, ether vapour is blown Into the 

 nerve chamber. The negative variation is tested for 

 at Intervals during the next two or three minutes ; it 

 is seen to diminish and to disappear. This abolition 

 of the negative variation by ether is not permanent ; at 

 the end of five or ten minutes the negative variation 

 reappears and gradually increases up to, and it may be, 

 beyond the normal. 



This experiment (fig. 8), which represents the 

 regular and unfailing consequence of the etherisation 

 of a nerve, proves that the electrical effect we are 

 dealing with is a physiological phenomenon. 



