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GEORGE SZÉKELY
tion of motoneurons with the corresponding muscles. Weiss (1941) had
already raised this question and offered an interesting suggestion. From
the finding that a supernumerary limb, innervated by the brachial cord,
moves in parallel with the normal limb on the same side, he introduced
the idea of myotypic modulation. By this is meant that each individual
muscle has some constitutional specificity by which it is distinguished
from all other muscles. The muscles impart their specificity to the
motoneurons via the innervating axons, and the modulated motoneurons,
in turn, become adjusted into the central action system according to their
specificity. As a final result, motoneurons with identical modulation will
deliver impulses simultaneously.
The experiments presented raise many questions and do not permit
an unambiguous interpretation. One fact seems to be established: namely,
that spinal cord segments at limb level possess a peculiar structure
determined in early embryonic life, and only this structure can move
the limb. If one tries to explain the identical rhythm of a grafted and
the normal brachial cord by assuming that identical cells of both brachial
cords are selectively linked with the corresponding neurons of a supraspinal center, the observed delay in the function of a grafted lumbosacral cord relative to the normal one immediately resists such an interpretation. Similarly, the fact that the character of the movements
is determined by the innervating segments is inconsistent with the
assumption that the motoneurons obtain their specificity by making
contact with the muscles. Furthermore, if the motoneurons were modulated by the innervated muscles and this were a major tool in the establishment of the appropriate motor and premotor connections, it would
be difficult to understand the well-known somatotopic representation of
muscles in the different nuclear subdivisions of primary motor centers.
These considerations make it unlikely that the structure of the limbmoving segments could be organized by selective synapsing mechanisms
which could link together the corresponding motor and premotor neurons
to deliver an appropriate output for limb movement on the basis of
inherent specificities, and which could match, at the same time, the
acquired specificities induced by the periphery. A more detailed elaboration of these questions is postponed for discussion in a forthcoming paper
devoted to the problem of locomotion.
C. The Functional Specificity of Cranial Sensory Ganglia
Following transection of the trigeminal nerve root in newts and frogs,
Sperry and Miner (1949) reported a complete recovery of skin sensation in the head region. They concluded that the sensory ganglion cells
of cranial nerve V which supply various sensory areas differ in charac-
GEORGE SZÉKELY
tion of motoneurons with the corresponding muscles. Weiss (1941) had
already raised this question and offered an interesting suggestion. From
the finding that a supernumerary limb, innervated by the brachial cord,
moves in parallel with the normal limb on the same side, he introduced
the idea of myotypic modulation. By this is meant that each individual
muscle has some constitutional specificity by which it is distinguished
from all other muscles. The muscles impart their specificity to the
motoneurons via the innervating axons, and the modulated motoneurons,
in turn, become adjusted into the central action system according to their
specificity. As a final result, motoneurons with identical modulation will
deliver impulses simultaneously.
The experiments presented raise many questions and do not permit
an unambiguous interpretation. One fact seems to be established: namely,
that spinal cord segments at limb level possess a peculiar structure
determined in early embryonic life, and only this structure can move
the limb. If one tries to explain the identical rhythm of a grafted and
the normal brachial cord by assuming that identical cells of both brachial
cords are selectively linked with the corresponding neurons of a supraspinal center, the observed delay in the function of a grafted lumbosacral cord relative to the normal one immediately resists such an interpretation. Similarly, the fact that the character of the movements
is determined by the innervating segments is inconsistent with the
assumption that the motoneurons obtain their specificity by making
contact with the muscles. Furthermore, if the motoneurons were modulated by the innervated muscles and this were a major tool in the establishment of the appropriate motor and premotor connections, it would
be difficult to understand the well-known somatotopic representation of
muscles in the different nuclear subdivisions of primary motor centers.
These considerations make it unlikely that the structure of the limbmoving segments could be organized by selective synapsing mechanisms
which could link together the corresponding motor and premotor neurons
to deliver an appropriate output for limb movement on the basis of
inherent specificities, and which could match, at the same time, the
acquired specificities induced by the periphery. A more detailed elaboration of these questions is postponed for discussion in a forthcoming paper
devoted to the problem of locomotion.
C. The Functional Specificity of Cranial Sensory Ganglia
Following transection of the trigeminal nerve root in newts and frogs,
Sperry and Miner (1949) reported a complete recovery of skin sensation in the head region. They concluded that the sensory ganglion cells
of cranial nerve V which supply various sensory areas differ in charac-