v SPINAL COED AND NERVES 341 



consciousness, arising from a psychical synthesis of elementary 

 sensations. 



Lastly, many of those who see in the co-ordinated spinal 

 reflexes inherited, instinctive, but unconscious acts, do not 

 recognise that in admitting these they implicitly admit a sort of 

 fossil intelligence for the cord, i.e. to adopt Bering's felicitous 

 expression unconscious memory of primitive psychical processes. 

 The entire i "soul" of a brainless Amphioxus is a spinal soul. 

 How much of this soul persists as such, and how much (to repeat 

 the metaphor) in a fossil state, in the spinal cord of the higher 

 vertebrates ? The future must decide. 



At first sight it would seem as though the most complex of 

 the spinal reflexes that are independent of the brain and, in our 

 opinion, indicate a rudimentary spinal intelligence, should be 

 more numerous, more striking, and better elaborated in the higher 

 animals with a more developed nervous system. The contrary, 

 however, is the fact ; these higher spinal reflexes predominate and 

 are more vigorous and pronounced in the lower vertebrates. This 

 of course may be due to the greater solidarity between the 

 different segments of the system in the higher vertebrates, and the 

 greater control exerted by the brain over the spinal mechanism, 

 owing to the development of the long spino-cerebral and cerebro- 

 spinal conducting paths which are totally absent in the lower 

 vertebrates. 



XII. The long conduction paths which run from the cord to 

 the brain and from the brain to the cord, constitute so many inter- 

 central reflex arcs, by means of which the spinal mechanisms of 

 the higher vertebrates are brought into direct functional com- 

 munication with the cerebral mechanisms. It is through these 

 long conducting paths that, with the development of definitely 

 conscious ^sensations and voluntary movements, the spinal cord 

 ceases to be a collection of autonomous centres and becomes an 

 instrument of the brain. 



We have seen that the cord is capable of executing perfectly 

 co-ordinated reflex movements. In voluntary movements impulses 

 descending from the brain throw the same spinal mechanisms into 

 play as are concerned in the execution of the spinal reflexes 

 excited by impulses conducted from the periphery along the 

 afferent nerves. Indeed, since reflex movements differ from 

 voluntary in nothing except the exciting agent, it would be 

 irrational to suppose that they depend on two separate central 

 mechanisms. 



Marshall Hall's theory, which distinguished the spinal reflexes 

 from the voluntary movements by assuming an excito-motor system 

 consisting of fibres separate from those of sensation and voluntary 

 motion, has long been abandoned. The anatomy of the cord shows, 

 as we have seen, that the same neurones, by coming into relation 



