THE ELECTRICAL RESPONSE. 



4*7 



Fin, 



variation. The observations extending over a period of two seconds, 



divided into ten parts, would represent an actual period of y!^ second, 



made up of successive periods of T oVo~ second. It is this method that 



Hermann has followed, with the important modification that instead of 



increasing the time-interval periodically, he 



increases it continuously and equably during the 



whole period. His period of excitation is also 



relatively longer, each hundredth of a second in 



the actual variation being represented by 3"-47 



second. 1 The process thus prolonged can be 



followed by a galvanometer with a light 



aperiodic magnet, so as to give a true graphic 



record of the variations. 



Observations were made both with uninjured 

 muscles, and with muscles of which the surface 

 of contact at the tendon end had been injured by 

 lunar caustic. By bringing together the two 

 curves a and b resulting from these observations, 

 so that they lie with corresponding points over 

 one another on the same axis, and drawing a 

 third curve c, any ordinate of which when 

 summed algebraically with the corresponding 

 ordinate of a would give the corresponding ordi- 

 nate of b, the combination reproduced in Fig. 228 

 was obtained, in which a represents the curve 

 of variation at the proximal electrode (the curve 

 of injury), b the diphasic curve of the uninjured 

 muscle, and c the (deduced) curve of variation 

 at the distal electrode. The figure shows that 

 the relative duration of the instrumental effect 

 of the first phase of the diphasic variation is 



considerably less than that of the monophasic variation. This, of course, does 

 not imply that the actual process which takes place at the proximal electrode 

 in the muscle itself is different in the two cases. 



In Fig. 229 I have endeavoured to show the time-relations of the same two 

 processes according to Bernstein's estimate of 

 the duration of each, represented on the same 

 scale as Hermann's curves, with the contacts 

 at the same distance from one another. The 

 reader will see at once that the difference 

 between them consists in this, that the dura- 

 tion of each phase is according to Bernstein 

 much shorter, and that, although the maxima 

 of the phases are about equal distance from 

 one another in the two cases, there is, according 

 to Bernstein's conception, an interval between 

 them during which the two contacts are equi- 

 potential, so that the curve is as it would 

 appear if the galvanometer were acted upon by 

 the summits of the waves only. 



We may now pass to the further knowledge which we are able to 

 obtain by means of the capillary electrometer. But in order to make 

 the experimental data on which that knowledge is founded intelligible, 

 it will be necessary to state shortly the principles by which observers 



1 Matthias, "Ueber graphische Darstellung der Actionstrbme des Muskels." Arch. 

 f. d. ges. Physiol., Bonn, 1893, Bd. liii. S. 72. 

 VOL. II. — 27 



228. — Curves of electrical 

 response to instantaneous 

 stimulation(gastrocnemius). 

 Contacts at 17 mm. dis- 

 tance on dorsal surface 

 and tendon ; x, moment of 

 excitation. The vertical 

 lines indicate hundredths 

 of seconds after x. a, curve 

 of response of injured 

 muscle ; b, diphasic curve 

 of uninjured muscle ; c, 

 derived curve of variation 

 at distal electrode. — From 

 Matthias. 



Fig. 229. — Diagram (by the writer, 

 not after Bernstein) represent- 

 ing the same phenomenon as 

 it would be if the duration of 

 each variation were -j^ sec. i, 

 interval between first and 

 second phases, a and e. 



