THE NEURONE 



467 



THE NEURONE. The 



nerve elements of the central, 

 as well as the peripheral, nerv- 

 ous system include the nerve 

 cells and the nerve cell proc- 

 esses; the latter are usually 

 called nerve fibres. This sub- 

 division, which has been hand- 

 ed down from former times, 

 when it was considered that 

 nerve cells and nerve fibres 

 were independent elements, is 

 still useful for descriptive pur- 

 poses. However, it must be 

 constantly borne in mind, and 

 can not be too often empha- 

 sized, that these two terms 

 are merely descriptive of two 

 portions of the same anatom- 

 ical unit, the neurone. 



Thus the neurone forms 

 the structural unit of the en- 

 tire nervous system. This 

 unit has already been dis- 

 cussed in its relation to the 

 nervous tissues,* but the im- 

 portance of a correct impres- 

 sion of its bearing on the 

 structure of the central nerv- 

 ous system as at present in- 

 terpreted, makes it advisable 

 at this time to briefly review 

 its structure. 



A neurone is an animal 

 cell. It consists of a cell 

 body (nerve cell, ganglion cell, 

 perikaryori) with all of its va- 

 rious processes. These proc- 

 esses include the dendrites, 

 which are considered as usu- 



FIG. 370. DIAGRAM OF A NEURONE. 



aft, axone hillock ; ax, neuraxis ; c, cyto- 

 plasm ; d, dendrites ; TO, myelin sheath of the 

 nerve fibre ; m', muscle fibre ; n, nucleus ; w', 

 nucleolus ; n. of n, nucleus of the neurilemma ; 

 nR, node of Ranvier ; s/, collateral ; sL, seg- 

 ment of Lanterinann ; tel, telodendrion. (After 

 Barker.) 



* See Chapter VIII. 



