Transplantation of the spinal ganglion, with observations on the significance of the complex types of spinal ganglion cells

One may no longer look upon the spinal ganglion as containing only simple unipolar cells with T-shaped axons.The researches of the past ten years have shown that from this fundamental type all sorts of variations occur.A glance at Dogiel's ('0s) monograph shows how great is the number of such variations and how completely they baffle any attempt at logical classification.From the cell body m.ay arise short, thick processes, or fine fibers ending in pyriform or spherical expansions.Other cells present elevated loops of protoplasm which are attached t o the cell body at both ends.When such loops are numerous, the cells are spoken of as fenestrated.In other cases the axon at or near its origin from the cell may be broken up into a number of fibers, which unite with each other to form a plexus, and which are finally assembled into a single axon.Other axons give off collaterals with terminal enlargements called end-bulbs.although these complicated structures have been much discussed, we are still in doubt as to their functional significance.In this connection, we should not forget that, although obscured by all these variations, the fundamental characteristic of the spinal ganglion cell remains unchanged; i.e., the cell possesses an axon which, dividing dichotomously, puts the cell into relation with the periphery on the one hand and the central nervous system on the other, and, so far as we understand the physiology of the spinal ganglion, this simple type seems to answer all the requirements for the conduction of afferent impulses.