Van Nouhuys1 has studied the structure of thirty-eight gasserian ganglions. He seems to have done this by observing in ganglions and sensory roots removed from cadavers of adults the course of the nerve fibers as seen by the naked eye or lens in more or less teased preparations. No study of the sensory roots by microscopic sections is reported. In none of the ganglions were there three anatomically separated parts in the sensory root that corresponded to the three terminal divisions of the fifth nerve. The appearance may have been deceptive. One might as readily expect to find the crossed pyramidal tract in the lateral column of the spinal cord anatomically entirely separated from the surrounding fibers, but because it is not one does not deny that this tract has a distinct function. In serial sections of the gasserian ganglion he found no indication that the cell groups represented