Abstract
There is a growing tendency to correlate physiologic with morphologic observations. This gives an important control to experiments requiring operation in which the damage to the central nervous system is often greater than the experimenter realizes. Similarly, in behavior studies, it is interesting to try to connect the appearance of a new pattern with the maturation of cells and fiber tracts in the nervous system. Just as with pathologic studies of nervous diseases, so here the staining methods are often inadequate for demonstrating the morphologic changes. In pursuing developmental studies the maturation of the cells as regards neurofibrils or granules might be observed. The formation of synaptic junctions cannot yet be accurately demonstrated. Myelinization of nerve pathways is one phase of maturation of the neuron that may be followed relatively easily. Myelinization has been used by me as an index of neuron maturity. Myelinization of the human central nervous system