Ranson, spinal Nerves. 1 07 



2. Classification of the spinal ganglio?j cells according to the 

 number and character of their processes. — Since in this paper we 

 are not directly concerned with the form of the spinal ganglion 

 cells, we need only mention the most important points under this 

 heading. That the cells of the spinal ganglion were all associated 

 with a single T-shaped process was the accepted view until 1896, 

 when DoGiEL published his important work on the form of the 

 elements in the spinal ganglion. To Dogiel belongs the credit 

 of having first clearly differentiated the following cells in the 

 spinal ganglia of mammals. 



A. Unipolar cells. Type I. The well known unipolar cells, 

 both large and small, with the .typical T-shaped processes of 

 Ranvier. 



Type II. A new form first seen by Dogiel, the single process 

 of which breaks up into numerous fine branches that end in peri- 

 cellular baskets within the ganglion itself. 



B. Bipolar cells — very few, only one or two in each ganglion. 



C. Multipolar cells with two nerve processes, one centrally, 

 the other peripherally directed, and many dendritic processes 

 arising from the angles of the irregularly shaped cell body. 

 These dendrites penetrate the capsule and end among the cells 

 of the ganglion. 



The observations of Dogiel were made upon preparations 

 stained by his modification of the methylene blue technique. 

 More recently ('05) Cajal has published a preliminary account 

 of his studies on the spinal ganglion with his new silver method. 

 One of his cell-types is distinctly new and may be described here 

 since it serves to emphasize the wealth of connections within the 

 ganglion. This is an unipolar cell, possessed of very fine den- 

 drites which take origin, sometimes from the surface of the cell 

 itself, sometimes from the origin of the axis cylinder. These 

 dendrites gradually enlarge and terminate in spheres, encircled 

 by an entire system of concentric capsules. These dendrites 

 sometimes bifurcate and give rise to a pair or more of terminal 

 globes. He distinguishes two varieties among these cells: in 

 one the terminal spheres are found beneath the capsule of the 

 cell of origin and are in relation with the pericellular "nests" of 

 Cajal and Dogiel, in the other the terminal globes are lodged 

 in the intercellular spaces sometimes far distant from their point 

 of origin. 



