SECT. III.] 



NERVOUS SYSTEM. 



221 



more, branched processes, which, at their origin, arc frequently 

 0"004'" to 0005'" thick, and can be followed for a distance of 

 01'" to o-2\'". These processes finally run out into fine fibrils, 

 which are scarcely thicker than crooo4-"', all lying in the grey sub- 

 stance. Besides these large multi-radiate cells, there occur in the 

 grey substance, and also in the substantia gelatinosa, other very 

 numerous but more isolated small cells between the nerve-tubes, 

 the signification of which it is difficult to ascertain in the actual 

 case. Some of them arc evidently nerve-cells ; others are no less 

 certainly merely plasm-cells, such as occur in connective tissue, 

 and belong to the stroma of that tissue, which is distributed 



Fig. 94. 



Large nerve-cells, with processes from the anterior horns of the human spinal 

 cord, magnified 350 times. 



throughout the entire extent of the spinal marrow, and supports 

 the nervous elements. 



The nerve-tubes of the grey substance arc extremely numerous, 

 constituting in every case the half, if not more, of it, and present 

 the same characters as those of the white substance, except that 

 they arc, on an average, only of half the diameter, or less (down to 

 o'ooo8'"). Still, just as in the white substance and the entering 

 nerve-roots, large fibres are also found here, especially in the ante- 

 rior horns, but more isolated, and particularly towards the anterior 

 roots. The investigation of the course of these nerve-fibres in the 



