SPINAL GANGLIA. Ill 



excretory vacuoles. Fig. 136 is a similar cell containing a reticular network 

 within its protoplasm. Nerve fibers branch over the outer surface of 

 ganglion cells, forming pericapsular and pericellular nets or baskets, 

 and have been said to penetrate the protoplasm. This, however, is denied, 

 and such formations as are represented by Fig. 136 are thought not to pass 

 outside of the cell. Ganglion cells often contain areas of yellow or brown 

 fatty pigment granules which increase with age. 



The results of special investigations of the course of the dorsal ganglion 

 fibers, made by the methylene blue method, are shown in the diagram, 

 Fig. 137. The large round cells (i) give rise to a single spirally twisted 

 process which begins at the apex of a conical elevation on the cell body. 

 The spiral fiber has a neurolemma and acquires a myelin sheath. It may 

 give off collateral branches (2). At the first or second node, sometimes 

 further on, it divides into 



77 7-, , 7 rr Nucleus. Nucleolus. 



a ceUuiipetai or afferent v 



branch, which is an axis 



cylinder with a per- **\ 



ipheral sensory ending, jm *'\ 



and a cellulifugal or fl *H 



efferent branchwhich V^ | / 



enters the spinal cord 



(Fig. in). Thecellulip- 



etal fiber may have a i ^ j%>^ 



branch in the dorsal ^ 



ramus and another in the f eath " c * naliculi r Reticubr apparatus. 



FIG. 135. SPINAL GANGLION FIG. 136. SPINAL GANGLION 



Ventral ramilS (2}' and CELL OF AN ADULT CAT. CELL OP A NEWBORN KIT- 



' \*J) al1 X 430. TEN. (Copied after Golgi.) 



the cellulifugal fiber may 



fork near the cell body (3) or at some distance from it (2). Besides the 

 large cells there are similar smaller ones, the fibers from which have little 

 or no medullary sheaths (4). It is to be noted that in all these forms the 

 cell bodies become virtually appended to single fibers, which in relation to 

 the central nervous system are afferent. 



A second type of cell, which occurs less frequently, is the round 

 unipolar form (6) the process of which divides into many medullated 

 branches. After losing their myelin these form pericapsular and peri- 

 cellular ramifications around the cell bodies of the first type. Each of 

 the latter is in relation with branches from several cells of the second type. 

 A third form is a multipolar cell with two medullated fibers which are 

 thought not to pass beyond the limits of the ganglion (7). 



Fibers from sympathetic cells enter the ganglion from the periphery 

 and branch about the blood vessels and cells of the second type. Through 



