1095 
the beginning of the footmovement be taken a point where the 
curve has risen about 1 millimetre, and a similar point on the 
KEREN t EI ene teh 
er erin ene er re en Aten neen tenere enten tenten tien tenen ien en Weren ten fie ftom fem | 
Shortening reflex in the tibialis anticus of a healthy 
man. 
Upper curve: displacement of the foot. 
Middle curve: thickening curve of tibialis anticus. 
Lower curve: time marks of 0.1 second. 
tibialiscurve as the commencement of the muscle-twiteih, the interval 
comes out as something between 0.028—0.032 second. | 
This fact points in the direction of a reflexphenomenon. If we had 
to deal with a voluntary contraction, the latent period would have 
been a great deal less constant. It is also a fact, that the interval 
between an external stimulus and the commencement of a voluntary 
movement is of the order of 0.12—0.15 second with a fairly expe- 
rienced subject. Constancy of this latent period is only to be expected 
with the most experienced subjects or after a special training. The 
latency of sensory reflexes is much more constant, but it depends in 
most cases chiefly on the intensity of the stimulus. The highest con- 
stancy is shown only in the deep reflexes, in which the intensity of 
the stimulus does not seem to possess any influence on the latency. 
The latent period of the superficial reflexes is generally of the order 
of 0.07—0.09 of a second, whereas the deep reflexes show a latency 
of the order of 0.035 second. With these figures we have to take 
into account that the latency is measured from the commencement 
of the stimulus until the commencement of the muscular response as 
indicated by the mechanical record. If we had recorded the current 
of action we should have found lower figures. 
In my experiments I was not able to get more exact or smaller 
