The spinal cord forms a great part of the central nervous system. This stimulated many workers to study its develop ment. The development of the spinal cord is the result of the proliferation, migration and differentiation of the neuroblasts. It arieses from a thickened area of the ectoderm (neural plate) which folds into a neural groove in the 12 days old embryo.
In the 14 days old embryo the neural folds fuse at the middle level of the embryo but cranially and . caudally the neural folds stay apart untill the age of 16 days when the neural folds are colsed at all levels. The growth of the neural tube takes place along the ventrodorsal and rostrocaudal axes. The gray matter of the spinal cord has been subdivided into cell columns depending on the aggregation of the cells. Four distinct stages in the development of cells and cell columns in the gray matter of the spinal cord of Boscat Rabbit are distinguished : Stage of differention, stage of the appearance of cell groups, stage of splitting and the stage of Nissl granule appearance. The cell groups in the rabbit are compared with those of other vertebrates.