Bauhaus-Universität Weimar

600 
FUNCTIONS OF THE BRAIN AND SPINAL CORD. 
It must not be imagined that during the state of fatigue of the 
central organs which returns every twenty-four hours, and during 
sleep, the brain and spinal cord become wholly inactive. The state 
of fatigue is certainly general, but the sensorium commune, that 
part of the brain on which the mind acts, is alone reduced to a state 
of especial inaction; the voluntary movements, only are wholly ar¬ 
rested during sleep. The action of all other parts of the brain and 
spinal cord is maintained as at other times. This is evident from 
the sphincters continuing to act, and from the persistence of the 
rhythmic movements of respiration, both of which sets of motions 
are dependent on true cerebro-spinal nerves. Certain muscles, 
therefore, although supplied by cerebro-spinal nerves, continue to 
act even during sleep; the sphincters are always closed, and the eye 
is always turned upwards and inwards, and the iris contracted, so 
that the pupil is narrow; the mouth, too, is usually closed during 
sleep. In short, we see that, even in sleep, the whole motor ap¬ 
paratus of the central organs, of the brain as well as of the spinal 
cord, is in an active state, and that merely the voluntary excitation 
of this apparatus is absent owing to inactivity of the sensorium 
commune. We must, therefore, suppose that during sleep the in¬ 
fluence of the central organs upon the sympathetic nerve is inter¬ 
rupted, for otherwise the power of that nerve to maintain certain 
movements would immediately begin to fail, as is distinctly seen to 
be the case in apoplexy, in syncope arising from affection of the 
central organs, and in the experiment of artificially destroying the 
spinal cord. 
3. Impressions conveyed by the sensitive nerves to the central organs 
are either reflected by them upon the origin of the motor nerves, without 
giving rise to true sensations, or are conducted to the sensorium com¬ 
mune, the seat of consciousness.—In the first case, the centripetal 
actions of the sensitive nerves merely excite the motor apparatus of 
the central organs, which has its seat principally in the spinal cord, 
but of which there are also ramifications in the brain; in the second 
case, the sensitive impressions are conducted to a particular part of 
the central organs without exciting reflex movements, and are taken 
cognisance of in the sensorium commune by the mind. Since the 
phenomena of reflection are not dependent on the sensorium com¬ 
mune, but on the motor apparatus of the central organs, and since 
this apparatus continues in activity during sleep, these motions take 
place then as well as in the waking state; as is proved by cough 
from irritation of the trachea, and many other phenomena which 
occur during sleep. 
4. The organic functions of the nerves are maintained in unim¬ 
paired force by the central organs of the nervous system.—In this 
respect the same relation prevails between the sympathetic nerve 
and the central organs as with reference to the motions of parts sub¬ 
ject to the sympathetic. The action of the organic nerves in regu¬ 
lating nutrition and secretion is, in a certain degree, independent. 
The nutrition of the embryo proceeds, even to the full period, 
though the spinal cord and brain be destroyed by disease (see page
        

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