329 
1893 - 94 .] Prof. Rutherford on Beaction Time. 
Tlie reaction times, as measured by the author’s methods, differ 
considerably from those of some German observers. In observations 
made on eight intelligent healthy men, varying in age from nineteen 
to sixty-two, the reaction time for sight varied from 0'1662 second 
to 0*2202 second, and was mostly between 0*20 and 0*22 second. 
The reaction time for hearing varied from 0*1448 second to 0*1930 
second, and was mostly between 0*15 second and 0*16 second. 
The reaction time for touch varied from 0*1416 second to 0*1906 
second in the different cases. The shortest time is that following 
stimulation of the cheek: it varied from 0*141 second to 0*157 
second. When the skin of a finger was stimulated the reaction 
time varied from 0*142 second to 0*190 second, but was mostly 
from 0*15 second to 0*18 second in the different cases. There 
was no evident relation between the age of the individual and 
the length of his reaction time. In a limb the reaction time is 
generally longer the greater the length of sensory nerve traversed 
by the impulse ; but there may be considerable variations in the 
reaction times for different districts in the field of touch that are 
not explicable by diff“erence in the length of sensory nerve traversed, 
but are probably due to difference in the closeness of relation 
between centres for tactile sense in the brain and the motor centre 
for the hand. It may therefore happen that a response is given 
sooner by the hand when its skin is stimulated, than when the 
mucous membrane of the mouth is stimulated, although in the latter 
case the impulse has a much shorter tract of sensory nerve to 
traverse. 
When the response is given by the right hand, the shortest 
reaction times for hearing and touch are obtained by stimulating 
the right ear and right cheek, so that the sensory impulse may be 
transmitted directly to the left side of the cerebrum, from which 
the motor impulse for the right hand emanates. In the experi- 
ments on sight, both eyes were used at same time. The influence 
of fatigue on the reaction time for hearing and the remarkable 
restorative effect of tea were demonstrated in photographs thrown 
on the screen. 
