96 NORMAL HISTOLOGY AND ORGANOGRAPHY. 



2. Dendrites, which are usually short processes, 

 very much branched, and physiologically carry an 

 impulse toward the nerve cell. A collection of 

 nerve cells constitutes a ganglion, while a nerve 

 plexus is a reticulum or interlacing of nerve fibers. 

 Nerve cells are classified, according to the number 

 of their processes, into unipolar, bipolar, and 

 multipolar. 



Nerve Cells. i. Unipolar nerve cells. These are 

 nerve cells with but one process. If a nerve cell 



Pat cells. 



Artery and vein. Bipolar nerve cells. 



Fig. 62. Section of spinal ganglion. 



has but one process that process must be an axis 

 cylinder. If a nerve cell has many processes only 

 one is an axis cylinder, the others are dendrites. 

 Unipolar nerve cells are found in the olfactory mucous 

 membrane. They are columnar or cylindrical and 

 each gives rise to a basal process, the axis cylinder, 

 which remains non-medullated and extends through 

 the cribriform plate to enter the olfactory lobe of the 

 cerebrum. This class of nerve cells is common in 

 invertebrates. 



