Effect of Medulla Transplantation.

Abstract

The experiments recently reported on the transplantation of parts of the central nervous system indicate that cellular hyperplasia can be induced in regions of the cord which normally have a low motor content. Heterotopic transplantations of the cord show conclusively that extensive hyperplasia, both motor and sensory, can be obtained. Previous experimentation by the author 1 has indicated that, with the cord in its normal location, there is a direct dependent relationship between the cellular content of the trunk segments of the cord and that of the regions anterior to it. These experiments are in direct confirmation of Detwiler's results. 2

The present series of experiments deals with the transplantation of an additional medulla just posterior to the normal medulla oblongata of the urodele embryo. A transverse section is made at the lower part of the medulla and the parts of the nervous system separated. The transplant which includes the ear capsules with the portion of the medulla in close association with them is then placed between the separated parts. The tissue contains Mauthner's cell area and the regions of the ninth and part of the tenth cranial nerves.

The transplanted ear capsules fuse with the normals, giving rise to a large mass of cartilaginous tissue which increases the proportions of the head and apparently permits the interpolated portions to develop. The ganglionic elements of the 9th and 10th fuse in a massive ganglion which is 40% larger than normal, but is smaller than the double ganglion content which would be expected. The nerves arising from the fused 9th and 10th form regular but enlarged trunks with regular distribution, containing, however, a greater number of fibers than are normally found in these nerves.