128 



NEKVOUS TISSUES 



from the base of a dendron, and passing for a considerable distance from 

 the cell body, finally enters the nerve fiber as its axis cylinder, or termi- 

 nates in relation to some distant 



JIL ^^^ nerve cell. This latter process is the 



^L ja&afe&SS^R axon. Each cell body usually pos- 



^^^B^B ' m^^^^ sesses a single axon and several den- 

 IJIJijjjjff drons. Cells without an axon are 



*^ Sr* found in the retina and in the ol- 



factory bulb; except for these, all 



f*jffij&gjjr nerve cells in the body of man pos- 



sess an axon and usually but one 

 such process. The subdivision of 

 nerve cells into uni-, bi-, and multi- 

 polar cells is, therefore, chiefly based 

 upon the number of their dendrons. 

 Dendrons (Dendrites, Protoplas- 

 mic Processes) . The dendrons of a 



FIG. 141. A NEURON (GIANT PYRAMI- 

 DAL CELL, OR CELL OF BETZ) FROM 

 THE CEREBRAL CORTEX OF MAN, 

 SHOWING THE NEUROFIBRILS. 



Bielschowsky technic. X 500. 



nerve cell vary from one to a consid- 

 erable number. They arise from the cell body by a broad stem, and 

 quickly' break into branches which can be traced for a considerable dis- 

 tance in fact, the arborization of the dendrons is usually so extensive 

 that it can be followed for only a short portion of its 

 course. Occasionally dendrons do not branch until 

 they have arrived at a considerable distance from 

 their parent cell-body. 



The structure of the dendron is, to all appear- 

 ances, similar to that of the cell-body. The chromo- 

 philic substance is continued for some distance into 

 the arborizing dendrons, which often possess a finely 

 fibrillar appearance. In Golgi-stained preparations 

 the dendrons frequently present a thorny appearance, 

 due to the clustering along their borders of minute 

 lateral projections, the gemmules. 



The terminal filaments of the dendronic arboriza- 

 tion are frequently in relation with the cell bodies 

 or axons of other neurons, less frequently with the 

 dendrons of other neurons. Such contact relation- 

 ship is known as synapsis. 



Dendrons are cellulipetal processes, transmitting impulses to the cyton. 



The Axon (Neuraxis, Neuraxon, Neurite, Axis Cylinder Process}. 



FIG. 142. INTRA- 

 CELLULAR NET- 

 WORK (TROPHO- 

 SPONGIUM) 

 WITHIN A PUR- 

 KINJE CELL OF 

 THE CEREBELLUM 

 OF Strix flam- 

 mea. 



Golgi's stain. (After 

 Golgi.) 



