The nervous system 



435 



neuro-fibrils previously spoken of. These pass from the dendrites 

 of the cell into the cell-body, and from the cell-body they 

 pass into the axon. The axon is therefore merely a bundle of 

 neuro-fibrils, a nerve is the immensely elongated process of a 

 nerve-cell. Cells with these processes vary in type and arrange- 

 ment, but may be classified into the two groups previously 

 mentioned of bipolar and multipolar. Bipolar cells are found 

 typically in the ganglia on the roots of the spinal and cranial 

 nerves. These cells are peculiar, inasmuch as they possess no 

 dendrite process. The axon issues as a single process from the 

 cell, and then divides T-shaped into two fibres (see Fig. 130) ; such 



Fig. 129. — Multipolar Nerve-Cell (Barker, after Kolliker). 

 n, Axon ; c c, collaterals ; d, dendrites. 



cells would have been called one-poled, but for the fact that 

 they are known by embryological studies to be bipolar. This 

 type of cell is especially associated with the sensory nerves, and 

 the axon is accordingly long, and may extend, say, from the foot 

 to the spinal cord. The multipolar cells (Plate I., 3, and Fig. 129) 

 are more widely distributed, and are found in the grey matter 

 of the brain and spinal cord. They are furnished with processes 

 and the usual axon, but the axon may be long or short, and this 

 peculiarity enables multipolar cells to be divided into two groups, 

 known as Golgi cells of the first and second type. Golgi cells 

 of the first type may have an actual or relatively long axis 

 cylinder. It may be a cylinder reaching from the cerebrum to 

 the medulla, which would be relatively long, or from a segment of 



