179 
1889 - 90 .] Dr Haycraft on Muscular Contraction. 
lated, the muscles contract but never smoothly, for local fascicular 
movement, as the author has elsewhere shown, always occurring. 
These cause the registering apparatus to oscillate at its own period, 
just as any swinging body may be kept in motion by occasional 
disturbances. We can thus explain how each observer obtained 
the same number of oscillations every time he stimulated the 
nervous system ; it was because he used the same recording 
apparatus each time. We can also see that the different periods 
observed by different observers are due to the fact that they each 
used a different recording apparatus. The author finds that on 
changing the recording apparatus (lever or tambour) the tracing 
obtained can be changed at will, and is practically a tracing of the 
oscillating period of the instrument used. 
On one occasion the author was stimulating the upper dorsal 
region of the cord of a rabbit thirty times a second, and was surprised 
to find that, in addition to the main oscillations of the tambour just 
described, there were finer oscillations at the rate of thirty a second. 
These disappeared on changing the tambour or on slowing the 
electrical interruptor, or on quickening its speed. They were evi- 
dently due to the tambour having some higher overtone of thirty a 
second at which it could oscillate ; why other observers had failed 
to obtain responses from the muscles synchronous with their stimu- 
lation period was because their levers and tambours w T ere unable to 
respond. While the author was unable to obtain curves showing 
a higher period than thirty a second, yet the stethoscope furnished 
evidence that changes go on within a muscle synchronous with stimuli 
applied at a much greater rate than thirty a second. When the cord 
or peduncles are stimulated one or two hundred times a second, the 
muscles respond by giving a note of exactly the same pitch. 
The ear gives better evidence of the nature of the muscular 
response than do such registering apparatus as tambours and levers. 
Nevertheless, if one is fortunate enough to get a tambour which has 
itself some period corresponding to the period of stimulation, it is 
quite capable of registering the effects which follow stimuli applied 
twenty or thirty times a second. If the tambours do not respond 
in the way indicated, they merely oscillate at their own slowest 
period. The oscillations are kept up in this case not only by such 
of the motions of the muscle, trembling at a quicker rate, as can 
