426 ANNUAL REPORT SMITHSONIAN INSTITUTION, 1914. 
In the same manner, if the strings of two violins are exactly tuned, 
then a note sounded on one will cause the other to vibrate in sym- 
pathy. We may likewise tune the vibrating writer V with a reed C. 
(Fig. 3.) Suppose the reed and the writer are both tuned to vibrate 
a hundred times per second. When the reed is sounded the writer 
will also begin to vibrate in sympathy. In consequence of this 
the writer will no longer remain in continuous contact with the 
recording plate, but will deliver a succession of taps a hundred times 
in a second. The record will therefore consist of series of dots, the 
distance between 
one dot and _ the 
next representing 
one-hundredth part 
of a second. With 
other recorders it is 
possible to measure 
still shorter inter- 
vals. It will now 
be understood how, 
by the device of the 
resonant recorder, 
we not only get 
rid of the error 
due to friction, but 
make the record it- 
self measure time as 
short as may be de- 
sired. The extraor- 
dinary delicacy of 
Fig. 3.—Upper part of resonant recorder (from a photograph). 
Thread from clock (not shown) passes over pulley P, letting down this instrument will 
recording plate. S’,screw foradjustment of distance of writing-point he understood when 
from recording plate. S, screw for vertical adjustment. T, tangent : : : 
serew for exact adjustment of plane of movement of recorder, parallel by 1ts means it 1s 
to writing surface. V, axis of writer supported perpendicularly at possible to record 
center of circular end of magnet. C, reed. M, micrometer screw for a time-int erval as 
adjustment of length of reed. aa ri the et) 
sandth part of the duration of a single beat of the heart. The com- 
plete apparatus for obtaining plant record is shown in figure 4. 
BY 
LY, 
COMPARISON BETWEEN SENSITIVENESS OF MAN AND PLANT. 
We have next to find some method of stimulation which will 
not cause any mechanical disturbance to the plant. In connection 
with this I made an important discovery which demonstrates the 
identical characteristics of excitation in plant and animal. In the 
animal tissue a constant electric current causes very characteristic 
