132 



PHYSIOLOGY OF CENTRAL NERVOUS SYSTEM. 



So far as the sensory fibers of the spinal and cranial nerves 

 are concerned, it is worth noting also that all of them arise from 

 cells lying outside the main axis of the central nervous system. 

 It has been a question whether the sensory impulses brought 

 to the ganglion cells through the peripheral process (sensory 



Fig. 60. Bipolar cells in the posterior root ganglion. Section through spinal gan- 

 glion of newborn mouse (Lenhossek) : a, The spinal ganglion; 6, the spinal cord; c, the 

 posterior, d, the anterior root. 



fiber) pass into the body of the cell before going on to the cord 

 or brain, or whether at the junction of the two processes they 

 simply pass on directly to the cord. According to the histo- 

 logical structure there is no apparent reason why an impulse 

 should not pass directly from the peripheral to the central 

 process at the junction, but whether or not this really occurs 

 and the relation of the ganglion cell to the conducting path are 

 questions that must be left unsettled at present. 



II. The multipolar cells. The processes of these cells fall into 

 two groups: the short and branching dendrites with an inner 

 structure resembling that of the cell body, and the axon or axis 

 cylinder process (Fig. 62). According to the structure of this last 

 process, this type may be classified under two heads : Golgi cells of 

 the first and the second type. The cells of the first type are charac- 

 terized by the fact that the axon leaves the central gray matter and 

 becomes a nerve fiber. This nerve fiber within the central nervous 

 system may give off numerous collaterals, each of which ends in a 

 terminal arborization. By this means the neurons of this type 

 may be brought into physiological connection with a number of 

 other neurons. This kind of nerve cell is frequently described 

 as the typical nerve cell. Golgi supposed that it represents the 



