The development of hippocampal and dorsolateral pallial regions of the cerebral hemisphere in fetal rabbits IV. Forty‐one millimeter stage, intermediate lamina

The structure of the cerebral hemisphere of the 41 mm rabbit embroy was studied with aniline and Golgi stains. Special attention was devoted to the intermediate lamina which forms the embryonic subcortical white matter. From Golgi preparations, two facts suggest that a simple plan underlies the distribution of most axons in this lamina: (1) axons of neuroblasts in the matrix and intermediate laminae turn in the lower part of this layer; (2) axons of neurons near the base of the cortical plate turn in the upper part of it. Since neuroblasts in the matrix and intermediate laminae are younger than cells forming the cortical plate, it is inferred that increments of growth occur along the lower surface of the intermediate lamina by the addition of new fibers. the factors which effect the growth of axons is not known, but it is possible that growth cones of some neuroblasts are guided through contact with previously formed horizontal fibers of this layer.