The development of muscle-spindles in the calf-muscles of the rat was followed under normal conditions and after section of n. ischiadicus. The first differentiation of muscle-spindles in the muscles of the hind limb of the rat was observed on the 19th day of intra-uterine development and their morphogenesis is complete by the 25th day after birth. After section of n. ischiadicus in rat foetuses on the 19th-20th day of intrauterine development, differentiation of muscle-spindles does not take place; neither intrafusal fibres nor the connective tissue capsule are formed. Since only proprioceptive fibres have innervated the normal muscle at this time, it is the loss of the morphogenetic influence of these nerve-fibres, that prevents differentiation. Similar results were obtained in rabbits denervated 7 days before birth. When section of n. ischiadicus is performed in new-born rats, disintegration of intrafusal fibres in which the equatorial segment was already differentiated at the time of denervation occurs within 10 days. Denervation in a 20-day-old rat, the muscle-spindles of which are already morphologically mature, leads after the same interval, to a slight atrophy in the equatorial zone of the intrafusal fibres. The mechanism of the morphogenetic influence of the nervous system and its changes during ontogenesis are discussed.
No takes yet. Share an insight, caveat, or question.
Jirˇina Zelena´ (1957) studied this question.
Synapse has enriched one closely related paper. Consider it for comparative context: