Bauhaus-Universität Weimar

INFLUENCE OF THE BRAIN AND SPINAL CORD 
201 
same result on repeating this experiment. The experiments which 
Bracket* and others have instituted on living animals, for the pur¬ 
pose of determining the irritability of the nerves, are of no value with 
regard to the heart, its action being so much affected by painful 
impressions. 
Another phenomenon which distinguishes the heart from other 
muscles is the persistence of its rhythmic contractions in thei^ regular 
order in the different cavities, even when removed from the body 
and emptied of its blood. This cannot be explained otherwise than 
by supposing the heart under these circumstances to retain with its 
nerves some specific nervous influence.t The influence of the nerves, 
therefore, seems to be the ultimate cause of the contractions of the 
heart; as the great effect which irritations of the brain and spinal 
marrow, and passions of the mind, have in modifying its action also 
tends to show. If it were possible to destroy the vital function of the 
nerves, without at the same time depriving the muscles of their 
power of contraction, this question might be set at rest; but unfor¬ 
tunately the narcotic agents, which, when applied to the nerves, take 
from them their property—when irritated—of exciting contractions 
in the muscles to which they are distributed, render the muscles in¬ 
capable of exercising their contractile power when the nerves are 
irritated. Opium applied to the heart of a frog soon puts a stop to 
its motion; this effect being produced, as Henry has shown, very 
rapidly when the narcotic is brought into contact with the inner sur¬ 
face of the organ, but more slowly when it is applied merely to its 
outer surface. It is evident, however, that the nerves have a great 
share in the heart’s action, from the sudden disturbance and cessation 
of the rhythmic movements when the whole spinal marrow is sud¬ 
denly destroyed. 
Influence of the brain and spinal cordon the hear Vs action.— 
The inquiry respecting the part of the nervous system whence this 
influence on the heart is derived, whether from the cardiac nerves 
and sympathetic system, or through the medium of these from the 
spinal marrow and brain, was originated by Bichat. Before entering 
into this inquiry, it will be necessary to give a sketch of the principal 
divisions of the nervous system. The functions of the two systems 
of nerves were more exactly defined by Bichat. The nerves arising 
from [connected with] the brain and spinal marrow have, for the 
most part, the power of exciting voluntary motion in the muscles to 
which they are distributed, but lose this power when their connec¬ 
tion with the nervous centres is cut off; and the nerves arising from 
the spinal marrow are also deprived of the power of communicating 
* Recherches sur le système ganglionaire. 
t Remak (Casper’s Wochenschrift, No. X. 1839) states, that the minute 
branches of nerves which he had traced into the muscular substance of the heart 
in man, as well as in many mammiferous animals, consist like other parts of the 
sympathetic nerve of the peculiar gray organic nervous fibres beset with small 
ganglia (see the fourth chapter of the second section in the book on the Nervqus 
System). And by the presence of these numerous ganglia, or centres, of nervous 
influence, he explains the continuance of motion in the „heart after its separation 
from the body. But it must be remarked, that Valentin denies the existence of 
these gangliated organic fibres.
        

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