138 Journal of Comparative Neurology. 



of a living rope by interlocking hands, the neurons unite 

 in chains serving to connect distant parts of the nervous 

 system. Each portion of the body has its representative 

 in some portion of the nerve tube (spinal cord and brain) 

 so that even in man a segmental or jointed character may 

 be ascribed to the nervous mechanism. These several seg- 

 ments are capable of acting independently of each other 

 and of consciousness, as may be demonstrated in reflex re- 

 sponses. The nerve paths are of two sorts, centrifugal 

 and centripetal, i. e. adapted to convey stimuli from and 

 toward the central organ. It is true also that in the nerv- 

 ous centres there are neurons concerned with the cen- 

 trifugal (motor) and centripetal (sensory) currents. It 

 appears certain that there is a permanent and important 

 difference in form and function between the kinesodic 

 (originative) and jesthesodic (receptive) centres and 

 systems. 



It is a remarkable fact that either of these systems 

 may be diseased within the spinal cord without affecting 

 the other. Thus in "tabes" all the sensory fibres of the 

 spinal cord may degenerate, destroying sensation, while 

 the muscular power is unaffected. 



In other cases descending degeneration may paralyze 

 groups of motor nerves while sensation is unaltered. Sen- 

 sations of heat and of pain may pursue other paths than 

 those of tactile sense. 



.While it is true that the spinal centres may act inde- 

 pendently it is also true that during normal states the 

 higher and especially the voluntary centres exert a remark- 

 able "inhibitory" control. The constant repressive, con- 

 servative action of the hemispheres is most important to 

 normal activity. 



In its relations to the body at large the brain and 

 central system is much more than the servitor of an active 

 intelligence, for throughout life there is a constant overflow 



