160 S. WALTER RANSON 
The ganglia were cut into sections 18 thick. It is difficult 
to make use of thicker sections because the silver method, unlike 
the intra-vitam use of methylene blue, brings out all the nerve 
elements so that very thick sections are confusing. On the other 
hand it is difficult except in thick sections to follow the axons 
to their bifurcation. 
Types of spinal ganglion cells according to external form 
1. The simple unipolar cell. From the body of a cell of this 
type arises a single axon, which after a longer or shorter, straight 
or convoluted course divides dichotomously into a thin fiber 
directed toward the spinal cord and a much thicker fiber running 
into the nerve. These represent, according to my observations, 
the great majority of the cells in the spinal ganglia of the dog. 
In sections 18, thick it is only in a small proportion of the axons 
that the entire course from cell body to bifurcation can be seen. 
For the most part it is possible to follow the axons for only a limited 
distance before they leave the level of the section. Many axons 
can be seen dividing but these can rarely be followed back to 
their cells of origin. Nevertheless this connection is so well 
established that it needs no confirmation. 
In the case of (a) the large cells, the axon is usually much 
convoluted in the immediate vicinity of the cell and within its 
connective tissue capsule, but in some cases the coil is wanting. 
In other cases the axon is very short and divides almost imme- 
diately after leaving the cell. These axons acquire a myelin 
sheath and stain by the pyridine silver method a light yellow. 
(b) All of the small cells and some of the medium sized ones 
present a different picture (fig. 1). The axon (whose thickness 
varies with the diameter of the cell) is thin and stains a dark 
brown or black. These axons seldom make complicated coils 
about the cells, but run more or less directly toward the central 
fiber bundles of the ganglia. Here these fibers can be seen in 
large numbers dividing in the manner of a 7 or Y into a very 
fine centrally directed fiber and a somewhat thicker one running 
toward the nerve (fig. 2). These branches together with others 
