Chap. XX VL] 



VOLUNTARY MOVEMENTS. 



565 



the same side in tlie ' 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 

 such Mechanisms 

 are continuous : and 

 these, traversing the 

 Motor Nerves at the 

 rate of about 111 feet per second, speedily excite definite 

 25 



Fig. 179.— Nerve Cell with many branches from 

 one of the anterior Cornua of a Hiiman Spinal Cord. 

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

 into, or joining the axis cylinder of one of the ' ante- 

 rior root ' fibres, the other processes being branched ; 

 b, an aggregation of pigment-granules on one side of 

 the large nucleolated nucleus, (x 150 diameters.) 



