Abstract
A piece of embryonic spinal cord, measuring 1 mm. to 1.5 mm, was transplanted, together with the surrounding tissues, in embryos of Discoglossus pictus, Otth., at the tail-bud stage. The transplantations were homoioplastic, and were made in the region of the hind limb. A histological study was made at or after metamorphosis.
Three forms of development took place, conditioned by the development of the tissues: (a) The grafted spinal cord developed independently of the homolateral hind limb, and these 2 organs had no mutual connections. (b) The transplanted tissues inhibited, through their own growth, the development of the homolateral hind limb. (c) Nervous connections occurred between the implanted spinal cord and the hind limb on the same side.
(a) The grafted spinal cord had a tendency to acquire a structure closely resembling that which it would normally have had. Motor-horn cells were irregularly distributed throughout, but there existed no distinct motor-horns. It gave rise to nerves which innervated the surrounding tissues. In one case where a nasal rudiment had been grafted anteriorly to the implanted spinal cord the latter sent forward a nerve which became fused with the olfactory organ.
(b) When the implanted spinal cord developed independently of the hind limb on the same side, the autochthonous spinal cord and its ganglia had a symmetrical structure. But in certain cases the implantation of the embryonic spinal cord inhibited completely the development of the homolateral hind leg. In such cases the lumbosacral plexus was not present on the affected side. The autochthonous spinal cord and its ganglia were asymmetric and had suffered a marked reduction on the same side, especially at the level of the segments which normally give rise to the lumbo-sacral plexus.
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