264 



SOME CHAPTERS ON THE 



of quartz silvered on the surface), moving up and down according 



to the current traversing it ; 

 the second line indicates the 

 respiration, inspiration mark- 

 ing upwards. A slow wave 

 of negative variation occurs 

 at each inspiration (indicat- 

 ing that an impulse passes 

 up the nerve at this time), a 

 conclusion arrived at on quite 

 other grounds by those who 

 have observed the pheno- 

 menon of respiration. 



There are many things of 

 interest to be observed in 

 studying this photograph. In 

 the first place, the curve is 

 a double one ; superposed on 

 the long respiratory waves 

 are shorter ones, the result 

 of the contractions of the 

 heart. Secondly, to any one 

 used to the study of the 

 negative variations recorded 

 by the capillary electrometer 

 two differences are most strik- 

 ing the E.M.F. of the current 

 and the time taken by the 

 wave. In Gotch's ( 16 ) analysis 

 of the electrometer curve the 

 E.M.F. of the negative varia- 

 tion in the sciatic of the frog 

 is -03 volt and the time 

 01 sec. ; here the E.M.F. of 

 the respiratory curve is 

 00005 volt and the dura- 

 tion 5 sees. The question 

 immediately presents itself 

 Are these phenomena, which 



alike have been called " negative variation," in reality the same ? 





