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figures for the latency. This was not due to the fact that I used a 
mechanically recording instrument, but only to the difficulty in deter- 
mining the exact moment of the stimulus. The stimulus is applied 
during the passive movement of the foot. But we cannot tell the 
exact moment at which the stimulus is produced. Must the foot move 
with a certain velocity or must it travel over a certain distance ? 
Perhaps both conditions are necessary. At least with a very slow 
movement of the foot we only obtain the tonus-thickening and with 
a very rapid movement over a short distance only, we sometimes 
fail and sometimes succeed in getting it. Therefore it is impossible 
to indicate the exact point in the record of the foot-movement which 
is to be considered as the beginning of the stimulus. If I take the 
first point in which both curves begin to rise from the zero-line, I 
find a latency from 0.038—0.045 of a second, with an average of 
0.041 second. If we take a rise of 1 millimetre in both curves as 
the beginning of the stimulus and the response, we get an average 
of 0.029 second. Though the exact figure is doubtful, it is yet of 
interest to note that it agrees closely with the average latency found 
in the deep reflexes. 
The duration of the muscular response has also to be considered. 
From direct observation and also from most of the records we come 
to the conclusion that we have before us a simple muscle-twitch, 
the duration of which is something between 0.2—0.5 second. Only 
in cases where the foot has been moved with great force, or has 
been kept in prolonged dorsal flexion, a muscular response of longer 
duration may be found. But in these cases the contraction shows a 
peculiarity, clearly visible in fig. 8, viz. a second contraction appear- 
ing before the first is finished. We shall consider this point later on. 
As from our observations we see that: 1ly the latent period is 
constant, 2y that the latency agrees with the latency observed in 
deep reflex, 3%y that the contraction is generally a simple muscle- 
twitch, we may conclude that the phenomenon itself is a real reflex. 
This being established we may ask where the reflexcentrum is 
situated, which is the reflexogene mechanism and which is tbe signi- 
ficance of the reflex. ; 
We may conclude from the latency that the reflexcentrum cannot 
be situated very high up in the central nervous system. I believe 
that another supposition as a medullary seat for the centrum need 
not be considered. The reflex has a close similarity to the deep 
reflexes and may probably be regarded as a third group of this kind, 
the other groups being formed by the tendonreflexes and the periost- 
reflexes. 
