V ANIMAL AUTOMATISM 221 



that what is true for man is true for other 

 vertebrated animals. 



We may assume, then, that in a living verte- 

 brated animal, any segment of the cerebro-spinal 

 axis (or spinal cord and brain) separated from that 

 anterior division of the brain which is the organ 

 of consciousness, is as completely incapable of 

 giving rise to consciousness as we know it to be 

 incapable of carrying out volitions. Nevertheless, 

 this separated segment of the spinal cord is not 

 passive and inert. On the contrary, it is the seat 

 of extremely remarkable powers. In our imagin- 

 ary case of injury, the man would, as we have seen, 

 be devoid 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 molecular 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 motor filaments, 

 reaches the muscles, which at once contract, and 

 cause the limbs to be drawn up. 



