Lippincott's Magazine of Popular Literature and Science, Vol. 26, November, 1880Various
History
Lippincott's Magazine of Popular Literature and Science, Vol. 26, November, 1880
Various
Literature, Modern -- 19th century -- Periodicals; Science -- Periodicals
Such are the phenomena which in the various species of animals follow
the removal of the true brain. Many of the acts are seemingly so
purposive, and certainly so complicated, as to suggest that they
must be conscious. It has, however, been shown that the fact that an
act is apparently purposive and complicated does not prove that it
originates in consciousness, and certainly in the brainless animal the
past, present and future have been blotted out. There is absolutely
no conscious memory, else the needed food would be taken when offered
and spontaneous movements would occur. It is hard to conceive of
consciousness without memory, and it is certain that no purposive
act can be directed by consciousness when memory does not exist in
any degree or form. If all memory be lost, though consciousness be
preserved, that consciousness would not have the knowledge which should
enable an animal to perform a complicated purposive act; nor could
it acquire knowledge by experience, because each movement would be
forgotten as fast as produced. The phenomena exhibited by the brainless
animals must therefore rest upon some other basis than consciousness.
The first point to be observed in looking for this basis is that
movements never occur so long as there is no external irritation. The
frog, the pigeon, the rabbit, all maintain the same absolute repose
unless the impulse comes from without. The fish is a seeming, but not
a real, exception to this rule. The frog, the pigeon, the rabbit,
all are quiet on the land, because their surface is not irritated:
the fish in the water rushes forward, because the play of the liquid
is all the time irritating the exterior of the body. Throw the frog
into the water, and it is seized with the madness of the fish; toss
the pigeon in the air, and it dashes forward; set the rabbit once in
motion, and its course also is a headlong fury. Placed under parallel
conditions, these various animals exhibit parallel phenomena, and
remain quiet unless disturbed by surface-irritations. The facts show
that for action in the animal whose upper brain has been removed some
external irritation must generate the impulse, which travels upward to
a nerve-centre, and then brings into activity certain masses of nervous
tissue (ganglia), which, thus aroused, send impulses out to the various
muscles without the intervention of consciousness. Movements generated
in this way are _reflex_ or _automatic_. In brainless[2] animals the
reflex actions are not different in their essence, but only in their
degree, from those performed in the frog with a cut spine; or, in other
words, the acts originating in the lower brain are reflex and similar
to those arising in the spinal cord, only more complicated and more
apparently purposive.
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