APPLICATIONS OF THE GRAPHIC METHOD. 191 
heart convey no current to the galvanometer ; but after section, 
as in the case of a skeletal muscle, the usual result follows. 
All observers, however, are agreed that a current is produced 
during contraction. Those not believing in that just referred 
to above (“current of rest”), term this one the “current of 
action”; while the other school names it the negative variation 
of the current of rest, inasmuch as the galvanometer needle 
swings in the opposite direction indicating, as they say, a 
diminution in the original current. 
The presence of this undisputed current can be made evident 
by a simple experiment, without the use of any of the elabo- 
rate apparatus noticed above. Let two frog’s limbs, with the 
@ 
Fig. 188.—Arrangement of parts to show Fig. 189.—The same when the primary cause 
secondary contraction in muscle is in nerve (after Rosenthal). - 
(after Rosenthal). 
nerves belonging to them, be prepared in good condition and 
arranged as in Fig. t88, so that the nerve of A rests along the 
thigh of B. On stimulating the nerve of B, the muscular effect 
in this limb is answered by asimilar onein A. That this is not 
necessarily due to escape of the current upon the nerve of A, 
may be shown by putting a ligature around the nerve of B below 
the point of application of the current and moistening it so as 
to allow of the free passage of the current. In such case stimu- 
lation of the nerve of B gives wholly negative results, because 
the ligature has destroyed physiological (molecular) continuity, 
though it does not prevent the passage of the current. More- 
