Abstract
In analyzing the so-called resonance phenomena of nervous control, discovered by the author, 1 the necessity arose to reinvestigate the problem of the significance of afferent excitations for the establishment and persistence of motor functions in Amphibia. In a number of toads and axolotls, limbs were de-afferented by removing all the spinal ganglia and attached dorsal roots of the limb segments (fore limb, hind limb or both), either on both sides or on one side only. In contrast to most of the earlier experiments, the operation was performed without opening the vertebral canal so that injury or degenerative damage to the motor roots could be strictly avoided. In one series the sympathetic system has been preserved, in another series it was removed within the de-afferented area, including ganglia and rami communicantes.
A. Experiments with toads. Twenty-eight animals were operated (in ether anesthesia) and examined as to their motor functions from immediately after the operation to 22 days later.
I. Motility. After bilateral de-afferentation of the hind legs (17 cases) no essential change from normal could be noticed in the performance of locomotor functions: jumping and walking on rough ground are well-aimed, well-coordinated and vigorous. The reflexes of righting, turning and wiping are performed in the normal way. The resting posture is normal, except for a certain lack of contact between the plantar surface of the foot and the ground. It is evident, therefore, that after de-afferentation the motor functions of the affected limbs persist without significant alterations. This is strikingly borne out by unilateral de-afferentation, no asymmetry in jumping, righting, etc., appearing in such animals.
No difference could be found in the motor functions between animals posqessing (14 cases) or deprived of (11 cases) the sympathetic chain.
De-afferentation of the fore limbs alone was effected in one case only.
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