146 EXPERIMENTAL PHYSIOLOGY 



CHAPTEE XV 



SOME EXPERIMENTS IN ELECTRO-PHYSIOLOGY 



That animal tissues are of themselves capable of producing currents 

 of electricity was first positively proved by Galvani's experiment of 

 contraction without metals, but our earliest accurate knowledge 

 relating to these currents is due to Du Bois-Eeymond, who first gave 

 us measurements of these currents, and taught us how best to study 

 them under different conditions. 



If a frog's muscle be excised — choosing one in which the fibres 

 run parallel to one another and to the surface of the excised muscle, 

 such as the sartorius or semimembranosus — and connected to a 

 galvanometer of high resistance by means of a pair of unpolarisable 

 electrodes, one being placed at about the centre of the longitudinal 

 surface and the other opposite a transverse section of the muscle 

 made by cutting across the muscle near one end, Du Bois-Eeymond 

 showed that a current was produced by the muscle, which passed, in 

 an outside circuit, from the longitudinal surface to the transverse 

 section, and in the muscle, from transverse section to longitudinal 

 surface. It was also shown that if the muscle were tetanised 

 the amount of this current underwent a change, and in the direction 

 of diminution. Du Bois-Eeymond termed the current obtained from 

 the resting muscle the natural current or current of rest, and the 

 alteration in it produced by stimulation the negative variation. Of 

 other workers who have added to our knowledge, Hermann stands 

 foremost, and is the author of the opposing view, which has steadily 

 gained ground until it is now almost generally accepted, that normal 

 muscle is iso-electric at all parts, and that it will only yield a current, 

 either when injured at some part, or on contraction. If one electrode 

 be connected to an injured part and the other to an uninjured, the 

 galvanometer will show a current passing from the uninjured to the 

 injured part. Or, again, if two iso-electric points be connected to the 

 galvanometer, and a muscle wave then started along the muscle, 

 the galvanometer will show a current passing from the resting part to 

 that in contraction. Further, a less injured or less active part is 



