AuGustT 10, 1899] 
NATURE 
345 
The Reflex Spasm.—We may now pass to reflex action, 
in which, since the motor apparatus of the card has to 
be first excited through a sensory nerve, the time which 
elapses before a response is evoked is necessarily longer 
than in the cases we have been so far considering. The 
by the alkaloid veratrine. So long as this is used in 
sufficiently small quantity (;gsoo Mgr. to a sartorius), its 
effect consists chiefly in the annulling of the unknown 
inhibitory mechanism, by virtue of which a muscle, after 
having responded to an instantaneous stimulus, at once 
returns to its previous state. Under 
Fic. 4.—The photographic curve of tetanus. 
period of excitation. 
response, if the motor cells of the cord have been 
rendered extra sensitive by a minute dose of strychnine, 
is a prolonged contraction [tracing of mechanical effect 
shown] the graphic of which is often indistinguishable 
from that of complete tetanus. When 
the electrical concomitants of such a 
spasm are recorded photographically 
(Fig. 6), it is seen that the curve 
resembles rather that of complete 
tetanus interrupted at regular inter- 
vals, than that of a series of responses 
to single instantaneous stimuli follow- 
ing each other at intervals of a tenth 
of a second or more. And by an- 
alysing the curve we learn that the 
difference which in the first instance 
comes into existence between the 
contacts, disappears and reappears 
rhythmically, and finally ceases. A 
single stimulus to the motor cells of 
the cord has therefore produced a 
series of short prolonged responses in 
the muscle, of which the rhythm is 
central, not muscular. ‘Vhe motor cell 
pours its influence on the muscle at regular intervals, but 
its effect each time is that of a continuous action. 
The property which a muscle has of, under ordinary 
experimental conditions, relaxing as soon as the exciting 
Fic. 5.—Tetanus of short duration, fullowed by another after 
muscle was not excited. 
cause ceases, appears at first to indicate discontinuity of 
voluntary action. We have, however, a means of re- 
moving this property without materially impairing the 
functional c capacity of the muscle. This means is furnished 
NO. 1554, VOL. 60] 
The radial indicates the be 
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an interval during w 
the influence of veratrine, when once 
started to work it is compelled to go 
on. [It was shown by graphic records 
that a muscle so treated can do as 
much work in response to a single 
instantaneous stimulus, whether in 
lifting heavy loads or in producing 
tension, as a normal muscle subjected 
to a series of instantaneous stimuli. } 
The electrical phenomena evoked by 
a single stimulus in a veratrinised 
muscle likewise show that the effect 
is absolutely continuous ; there is no 
trace of unevenness or undulation in 
the photographic curve (Fig. 7), the 
contour of which resembles the general 
contour of artificial tetanus, ze. a 
sudden difference of potential comes into existence at 
the moment of excitation, but, notwithstanding that it is 
evoked by an instantaneous stimulus, it persists as if it 
were the response to a continuous one. 
ginning of the 
Fic. 6.—Reflex response of sartorius to nstantaneous excitation in strychnised preparation. 
To complete the subject, it is necessary to describe the 
electrical phenomena which accompany the action of the 
heart. In all that has preceded, a parallel-fibred muscle 
has been employed in which the excitatory wave 
propagated along the fibres in two 
opposite directions only. In the heart 
is 
the fibres are short, and run in all 
directions. The wave of excitation 
may originate anywhere, and may 
spread in any direction. We employ 
the ventricle of the heart of the frog, 
having first arrested its rhythmical 
beat by a ligature between sinus and 
auricle. We can then evoke a con- 
traction by an instantaneous excitation 
at any part of its surface, and thus 
imitate the first fundamental experi- 
ment in muscle. At the excited point 
the surface becomes instantly negative 
to all other parts, and the state of 
relative negativity spreads radially 
just as in muscle it was propagated 
longitudinally, the electrical effect 
appearing to precede the mechanical. Moreover, the 
duration of the process is ten times as long, and the 
rate of propagation ten times as slow. But in other 
respects the two processes in cardiac and skeletal muscle 
hich the 
