1888 - 89 .] Dr A. James on Muscle Contraction. 387 
movement, and the interval was found to be • 05 second. It was 
observed, further, that with each tap of the supinator longus tendon 
a contraction of the biceps muscle occurred. This was also timed 
by means of tambours employed in a similar way, the button of the 
receiving one being held in contact with the middle of the muscle. 
The interval between the tap on the supinator longus tendon and 
the contraction of the biceps was found to be - 045 second (see 
Tracing III.). 
Ankle Clonus . — The method by which this was timed was the 
ordinary one, and is so well known that it need not be described. 
The rate of the clonus was found to be in both legs about 7 per 
second (see Tracing IV.). 
Knee Clonus . — This could be easily induced in both legs by 
drawing down the patellae, and was timed in the ordinary way. 
The rate was found to be about 8 \ or 9 per second (see Tracing IV.). 
From these data the following conclusions may, I think, be 
drawn : — 
I. That (as has been pointed out by other observers) the interval 
between the tap on the tendon or muscle and the resulting move- 
ment is too short to enable us to regard these jerks as being ordi- 
nary reflexes in which sensory nerves, nerve centres, and motor 
nerves are together concerned. Thus in this patient the plantar 
reflex was found to be T6 second, and the Achilles tendon jerk 
*08 second. Were both of these similarly produced reflexes, the 
latter would have taken as long, or even a longer, interval to occur 
instead of a much shorter one. 
II. That yet these muscle or tendon jerks cannot be regarded as 
direct contractions. In evidence of this is to be noticed — 
(a) That the interval between the tap and the resulting contrac- 
tion differs in different muscles, being greater in the case of the 
gastrocnemius than in the quadriceps femoris, and greater in the 
quadriceps femoris than in the supinator longus. Were they direct 
we should expect the interval to be the same or nearly the same in 
all. 
(I further found in this patient that with single induction shocks, 
as stimuli applied directly to the muscles, the contraction of the 
gastrocnemius took place more rapidly than that of the quadriceps. 
In the tracings given the interval was in the case of the quadriceps 
