CHAP. XXVI.] VOLUNTARY MOVEMENTS. 



56-5 



the same side in the * anterior column.' The motor fibres 

 which decussate and pass downwards in the lateral columns 

 of the Spinal Cord 

 enter the anterior 

 cornua of Grey Mat- 

 ter in the cervical, 

 the dorsal or the 

 lumbar region, ac- 

 cording to the situa- 

 tion of the groups 

 of cells concerned 

 with the Movements 

 which the particular 

 cerebral stimuli tra- 

 versing these chan- 

 nels are destined to 

 evoke. 



The passage of 

 Cerebral incitations 

 or stimuli through 

 one or other of these 

 Spinal Mechanisms 

 is followed by an 

 outpouring of grad- 

 uated Molecular 

 Movements along 

 certain of the fibres 

 of the ' anterior 



roots ' with Which FIG. 179.- Nerve Cell wilh many branches from 



such Mechanisms e of * c l ! nte . rior 9. 01 ? ua 5 a . ^ uman Spinal Cord ' 



(Max Schultze.) a, Unbrancned Cell-process passing 



are COntinUOUS : and into, or joining the axis cylinder of one of the ' ante- 

 . i , , -1 rior root ' fibres, the other processes being branched ; 



S6, Liavei ^ ^ an aggregation of pigment-granules on one side of 



Motor Nerves at the th e large nucleolated nucleus, (x 150 diameters.) 



rate of about 111 feet per second, speedily excite definite 



