30 
spinal marrow destroyed, the stomach was 
violently crushed with a hammer. The heart, 
which previously beat vigorously sixty times in 
a minute, stopped suddenly and remained 
motionless for many seconds. It then con- 
tracted;—after a long interval it contracted 
again, and slowly and gradually recovered an 
action of considerable frequency and vigour.’”* 
Dr. W.C. Henry has added an argument in 
favour of the theory of neuromyic action of ano- 
ther kind. It is known that certain narcotics, 
applied to nerves, destroy the vis nervosa of 
that part. Dr. Henry found that “ a solution 
of opium injected into the cavities of the heart, 
or introduced into the intestine, immediate] 
arrested the actions of these organs.”+ it 
seems difficult to imagine that this effect of 
the narcotic was not produced through the 
medium of the nervous fibrille, the muscular 
being defended by the internal lining of these 
organs respectively, in the latter organ,a mucous 
membrane. 
After much consideration given to this 
subject, we should be disposed to conclude 
that in the phenomena of muscular action, the 
stimulus acts upon the nervous fibre, and that 
the contraction is an effect and the property of 
the muscular fibre. 
If this view be correct, we are necessarily 
led to consider the vis insita, or muscular 
wer, in connection with the vis nervosa. 
is latter power is peculiar to certain of 
the nervous system. It is not possessed by the 
cerebrum or cerebellum, or by the ganglia; but 
it exists in the tubercula quadrigemina, the me- 
dulla oblongata, the medulla spinalis, and the 
muscular nerves. The heart itself has recently 
been observed by Burdach to contract on sti- 
mulating the ceatiea nerves by galvanism. 
We owe the discovery of the distinct limita- 
tion of the vis nervosa, or, as he terms it, the 
“ excitabilité,” to M. Flourens.} 
The following were the supposed Jaws 
of action of the vis nervosa by Haller, Bichat, 
and Professor Miiller, before I began my own 
researches on this subject: 
Haller observes, “ Irritato nervo, convulsio 
in musculo oritur, qui ab eo nervoramoshabet.” 
“ Trritato nervo, multis musculis communi, 
totive artui, omnes ii musculi convelluntur, qui 
ab eo nervo nervos habent, sub sede irritationis 
ortos. Denique medulla spinali irritata, omnes 
artus convelluntur, qui infra eam sedem nervos 
accipiunt; megue contra artus, qui supra 
sedem irritationis ponuntur.” He concludes, 
“ conditio illa in nervo, que motum in muscu- 
lis ciet, desuper advenit, sive a cerebro et me- 
dulla spinali, deorsum, versus extremos nervo- 
rum fines propagatur.” And—“ ut adpareat 
causam motus a trunco nervi in ramos, non a 
ramis in truncum venire.”’§ 
Bichat observes, “ l’influence nerveuse ne 
se propage que de la partie supérieure a |’in- 
férieure, et jamais en sens inverse. Coupez un 
* Op. cit. p. 160. 
t Abstracts of a tread before the Royal 
Society, vol. iii. p. 60. 
t Op. cit. p. 16, &e. 
§ Elementa Physiologie, Lausanne, t. iv. p, 335. 
IRRITABILITY. 
nerf en deux, sa partie inférieure irritée fera” 
contracter les muscles subjacens; on a beau 
exciter l’autre, elle ne détermine aucune con- 
traction dans les muscles supérieurs ; de méme 
la moélle, divisée transversalement et agacé€ 
en haut et en bas, ne produit un effet ser 
que dans le second sens. Jamais l’infl 
nerveuse ne remonte pour le mouven 
comme elle le fait pour le sentiment.” * 
Lastly, Professor Miiller observes, “ the 
motor power acts only in the direction of the 
primitive nervous fibres going to muscles, ori 
the direction of the branches of the nerves ; and 
never backwards ;’ and “ all nervous fibre: 
act in an isolated manner from the trunk of @ 
nerve to its ultimate branches.” + .@ 
It is a singular circumstance, that an esta- 
blished fact in experimental research, an esta- 
lished principle of muscular action in t 
animal economy, should be without a) tion 
to physiology. Yet such has been case. 
For what is the application of the vis nervosa 
to the explanation of the functions of the ani 
ceconomy ? 
Before any such application could be made 
it was n that other modes of action 
this power should beascertained. I have, by a 
series of experiments, determined new laws of 
action of the vis nervosa, and have thus t 
enabled to make an extensive application © 
the principle to the functions of like ' 
The head of a river tortoise being separates 
between the third and fourth vertebra : 
1. The dorsal portion of the spinal marrow 
was laid bare to the extent of one inch below 
the origin of the brachial nerves; the spin 
marrow was then excited by means of th 
probe and by galvanism; both anterior 
posterior extremities, with the tail, were mover 
2. A lateral intercostal nerve was then laid 
bare, and stimulated in the same manner ; the 
same effects were produced as in the former 
experiment. 
These experiments have been Yr 
times, and I performed them in the presence 
of M. Serres and other gentlemen at Paris, in 
the month of August, 1839. They establish 
the following new laws of action of the v 
nervosa :— > *’ 
1. That it does act in the direction 
branch to trunk ; " 
2. That it is in a retrograde direction in th 
spinal marrow. “ 
The application of these new laws to ph; 
siology—the first application of the vis nerve 
to physiology—is very extensive, co-extens 
indeed with all the acts of ingestion ar 
egestion in the animal economy. But it doe 
not belong to our present article to treat of th 
important and extensive subject. We no 
return to that of irritability in general. 
The degree of irritability is not the same i 
every organ of the body. Haller and Nysten 
have investigated this subject, and the follow. 
ing are their statements respectively : 
Haller observes, “ Tenacissima virium in 
* Anatomie Générale, 2de ie, t. iii, p. 277. 
278, éd. 1801. ee ae , 
t Handbuch der Physiologie, i. 656. 
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