ELEMENTS OF NERVOUS TISSUE. 63 



fact, as to have led some to doubt its existence. 

 They contain a pale, finely granular substance, toge- 

 ther with a variable amount of pigment, as a general 

 rule (PL XIII. fig. I. 6). The nucleus is spherical in 

 shape, and much more distinctly marked in its out- 

 line than the cell itself, and amongst the granules 

 which it contains the nucleolus is readily distin- 

 guished by an unusual degree of brilliancy. In the 

 ganglia there are some cells which, outside of their 

 own proper cell-wall, are enveloped by another, a 

 second and much thicker envelope, consisting of 

 structureless or very delicately fibrillated material, 

 full of oval nuclei (PL XIII. fig. I. 8). This seems 

 to be partially developed connecting tissue belonging 

 to the proper stroma of the organ. 



In regard to their form, nerve cells are either ^ape of nerve 

 simply spherical, or furnished with one, two, three 

 or more, tubular prolongations of their cell walls (PL 

 XII. fig. VI. ; PL Xllirfig. I). The spherical cells 

 seem to be merely in contact with the neighboring 

 nervous elements amongst which they are situated ; 

 but the multipolar or caudate cells are continuous, 

 by their prolongations, with nerve fibres, or their 

 caudate processes anastomose with each other, as can 

 be readily seen in the grey matter of the cerebellum. 



Nerve cells, associated with other elements, are Distribution, 

 found in the grey matter of the cerebro-spinal axis, 

 and in the ganglia of the cerebro-spinal nerves and 

 those of the great sympathetic. They are also found 

 in the nerves which traverse the substance of organs, 

 in which they form microscopic ganglia. Finally, as 

 we have already intimated, the nervous fibres of the 



