320 



NERVE-CELLS. 



developed nerve-cells. In the case of the bi-polar cells, especially those of a spindle- 

 shape with a process from either end, both these processes are prolonged as nerve- 

 fibres (fig. 370) : from another point of view the cell might be looked upon as a 

 nucleated enlargement interpolated in the course of the fibre. In other bi-polar 



Fig. 371. GANGLION-CELL OF A FROG, HIGHLY MAGNIFIED (Beale). 

 a, a, straight fibre ; 6. b, coiled fibre ; c, smaller coiled fibre joining it. 



Fig. 372. RAMIFIED NERVE-CELL FROM ANTERIOR CORNU OF SPINAL CORD OF MAN 



(from Gerlach). 



a, axis-cylinder process. 6, clump of pigment granules. Above the cell is 

 seen part of the network of fibrils mentioned in the text (p. 322). 



Fig. 373. AXIS-CYLINDER PROCESS OF A NERVE-CELL (M. Schultze). 

 x , x , Portion of nerve-cell from spinal cord of ox, with axis-cylinder process, 

 a, coming off from it and acquiring at a' a medullary sheath. Highly magnified. 



cells in which the processes come off on the same side of the cell, the latter often 

 has a pyriform shape (fig. 371), the fibres being prolonged from the stalk of the 

 pear and the nucleus of the cell being placed in the larger end. As was shown by 

 Beale, a peculiar arrangement of the two fibres which are thus prolonged from these 

 pear-shaped cells is found, the one being generally coiled spirally round the other 

 for a certain distance, after which the fibres separate and take opposite directions. 

 The spiral fibre has been described as breaking up into an interlacement of fine 

 fibrils upon the surface of the cell. An indication of this is represented in fig. 371. 



