226 AimfAL AUTOMATISM. 



of extremely remarkable powers. In our imaginary 

 case of injury, the man would, as we have seen, be de- 

 void of sensation in his legs, and would have not the 

 least power of moving them. But, if the soles of his 

 feet were tickled, the legs would be drawn up, just as 

 vigorously as they would have been before the injury. 

 "We know exactly what happens when the soles of the 

 feet are tickled ; a molecular change takes place in the 

 sensory nerves of the skin, and is propagated along them 

 and through the posterior roots of the spinal nerves, 

 which are constituted by them, to the grey matter of 

 the spinal cord. Through that grey matter, the molecu- 

 lar motion is reflected into the anterior roots of the 

 same nerves, constituted by the filaments which supply 

 the muscles of the legs, and, travelling along these mo- 

 tor filaments, reaches the muscles, which at once con- 

 tract, and cause the limbs to be drawn up. 



In order to move the legs in this way, a definite co- 

 ordination of muscular contractions is necessary; the 

 muscles must contract in a certain order and with duly 

 proportioned force ; and moreover, as the feet are drawn 

 away from the source of irritation, it may be said that 

 the action has a final cause, or is purposive. 



Thus it follows, that the grey matter of the segment 

 of the man's spinal cord, though it is devoid of con- 

 sciousness, nevertheless responds to a simple stimulus 

 by giving rise to a complex set of muscular contractions, 

 co-ordinated towards a definite end, and serving an obvi- 

 ous purpose. 



