202
GEORGE SZÉKELY
of the ganglion cells means merely that impulses carried by vagus or
trigeminal fibers differ from each other in some of their physiological
characteristics, then a continuous barrage of impulses from the nonstimulated ganglion could facilitate the effect of impulses bearing the
same physiological character. This would make it understandable that
the vagus motor nucleus could be discharged with equal probability from
the cornea whether there are two vagus ganglia or two trigeminal ganglia
on the same side.
This quantitative aspect in the establishment of new reflex relations
seems to gain support from recent observations. The irregular reflexes
were yielded only by slightly more than one-half of the operated animals,
and this proportion could not be improved by doing the operation on
increasingly older animals up to midlarval stage (Straznicky, unpublished observations, 1963). Therefore, a progressive determination could
not be shown. The necessity for the presence of two similar ganglia on
the same side in order to establish new reflex relations is indicated by the
experiment in which the two ganglia were interchanged in the same
animal. Out of twenty-six animals, two yielded definite gill reflexes and
three more showed just a slight gill movement to the stimulation of
the cornea. The quantitative aspect in the establishment of a gill reflex
from the cornea in animals bearing two vagus ganglia is probably most
convincingly demonstrated by the observation that the gill reflex cannot
be evoked from the cornea following anesthetization of the posterior head
region, while both the afferent and efferent limbs of the reflex remain
intact. This failure to evoke the reflex can be shown by preventing a
small region of the normal vagus area from becoming anesthetized, so
that the gill reflex could then readily be evoked from this part. The
sensitivity of the cornea was indicated by a slight eye withdrawal upon
touching the cornea—a reflex normally present in the second half of the
larval period.
In conclusion, it can be stated that behavioral studies of reflexes in
the head region give very little information about the underlying nervous
mechanism. It is probable that the above suggestion is just as incorrect
as the assumption of selective synaptic connections governed by neuronal
specificity. Only a thorough electrophysiological study can throw more
light on these problems.
III. Acquired Specificities
In this section are collected those experimental findings which have led
to the conclusion that the specific qualities of some neurons have developed under the influence of the peripheral tissues they happened to
innervate. The basic experiment leading to this conclusion was that
GEORGE SZÉKELY
of the ganglion cells means merely that impulses carried by vagus or
trigeminal fibers differ from each other in some of their physiological
characteristics, then a continuous barrage of impulses from the nonstimulated ganglion could facilitate the effect of impulses bearing the
same physiological character. This would make it understandable that
the vagus motor nucleus could be discharged with equal probability from
the cornea whether there are two vagus ganglia or two trigeminal ganglia
on the same side.
This quantitative aspect in the establishment of new reflex relations
seems to gain support from recent observations. The irregular reflexes
were yielded only by slightly more than one-half of the operated animals,
and this proportion could not be improved by doing the operation on
increasingly older animals up to midlarval stage (Straznicky, unpublished observations, 1963). Therefore, a progressive determination could
not be shown. The necessity for the presence of two similar ganglia on
the same side in order to establish new reflex relations is indicated by the
experiment in which the two ganglia were interchanged in the same
animal. Out of twenty-six animals, two yielded definite gill reflexes and
three more showed just a slight gill movement to the stimulation of
the cornea. The quantitative aspect in the establishment of a gill reflex
from the cornea in animals bearing two vagus ganglia is probably most
convincingly demonstrated by the observation that the gill reflex cannot
be evoked from the cornea following anesthetization of the posterior head
region, while both the afferent and efferent limbs of the reflex remain
intact. This failure to evoke the reflex can be shown by preventing a
small region of the normal vagus area from becoming anesthetized, so
that the gill reflex could then readily be evoked from this part. The
sensitivity of the cornea was indicated by a slight eye withdrawal upon
touching the cornea—a reflex normally present in the second half of the
larval period.
In conclusion, it can be stated that behavioral studies of reflexes in
the head region give very little information about the underlying nervous
mechanism. It is probable that the above suggestion is just as incorrect
as the assumption of selective synaptic connections governed by neuronal
specificity. Only a thorough electrophysiological study can throw more
light on these problems.
III. Acquired Specificities
In this section are collected those experimental findings which have led
to the conclusion that the specific qualities of some neurons have developed under the influence of the peripheral tissues they happened to
innervate. The basic experiment leading to this conclusion was that