OF THE NERVUS OGTAVUS. 159 



attic displaces, it is very curious to see how people are thrown 

 topsy turvy - though the floor does not move - - and how their 

 equilibration is disturbed, now that unusual optico-motor impul- 

 ses are giving unusual irritation to the muscles of the eyes and trunk. 



Optic impulses, when moving, greatly influence the movements 

 of the eyes and the trunk. 



Not only labyrinthic, but also optic and kinaesthetic afferent 

 impulses are excercising a permanent control upon those movements 

 in order to fulfil the purpose of maintaining the equilibrium. But 

 this coordinate action is an automatic one. 



There are no arguments to accept , that it is produced by an 

 organon perceiving equilibrium and , after perception , correcting con- 

 sciously the perceived faults in aequilibration. 



The customary position of our body being regulated in the same 

 way, by the same sensu-motor automatic innervations, there remains 

 a large problem for anatomical investigations to elucidate the paths, 

 by which the impulses parting from the periferical endings are 

 directly and indirectly conducted towards defined motor nuclei. 



As far as our knowledge goes till now, they do not pass through 

 the cortex. Their being subcortical paths can be proved. 



But if - - as may be probable - - the cortex should perceive the 

 subcortical innervations, taking place in that extensive complex of 

 tracts and centres, such a perception should be sought in the 

 psycho-motor area of the cortex. 



Not only EWALD'S experiments point to this view. 



There may exist a perception of the summary of all octavo-motor, 

 optico-motor and kinaesthetic innervations, balancing each other and 

 maintaining a resultant motor-innervation as a very vague sensation, 

 not clear enough to speak to consciousness as the common sensory 

 perception does. 



Every sudden and important change in the whole of these sub- 

 cortical innervations must necessarily cause disorders in the customary, 

 resultant motion or position, but on the other hand they may be 

 the cause of a more or less intense perceived desorientation of these 

 somato-psychic functions. The expression, we are accustomed to use 

 in order to indicate every somato-psychical desorientation of this 

 kind, is dizziness" or vertigo". 



Therefore the vertigo is not the origin of motor disturbances, 

 but every sensu-motor disorder of this kind may awake the somato- 

 psychical desorientation, called vertigo. 



All these questions however; whether there exists a perception 

 of equilibrium? how that perception is altered? what vertigo may 



