904 HANDBOOK OF PHYSIOLOGY ^ NEUROPHYSIOLOGY II 



FIG. 13. Model of telcocinetic 

 and ereismatic motility. Three 

 persons represent the actions and 

 reactions involved in an inten- 

 tional motor performance. The 

 'telcocinetic' leaper (/) is sup- 

 ported by the 'ereismatic' carrier 

 (,2) and supporter (j). a to c. 

 The leap succeeds when the 

 ri^ht support is given and when 

 the carrier knows the moment at 

 which / jumps, d to/; The same 

 leap without supporting activity 

 fails. The unsupported and un- 

 prepared carrier falls backward 

 and is only caught by emergency 

 action of 5. The leaper jumps too 

 short and also falls because of 

 lack of the proper support. (Re- 

 drawn from an unpublished 

 motion picture made by Hess in 

 >943> 



tions are recruited when the lower mechanisms be- 

 come insuiScient and falling is imminent. The precise 

 mechanisms of these extrapyramidal postural regula- 

 tions and their relation to teleokinetic motor activity 

 need more experimental study. 



Some essential differences between the head and 

 eye movements of man and those of quadruped 

 mammals are important for the understanding of 

 extrapyramidal direction-specific responses, a) In 

 man, eye movements are more prominent and used 

 more frequently than in animals mainly moving the 

 head. Cat optomotor reactions concern the head more 

 than the eyes, h) The various planes of inovement and 

 the spatial relations of the eyes, head and trunk are 

 different in man and quadrupeds. The upright posi- 

 tion of man and the position of his head and eyes 



relative to his trunk requires a totally different motor 

 organization. Therefore it is not permissible to 

 homologize Hess" findings in the cat with the condi- 

 tions in man [Jung (132)] since the eye mo\'ements of 

 these two species are similar onlv relative to the head. 

 In man, a turning mosement in the horizontal plane 

 is effected bv rotation of the head and eyes relati\'e to 

 the trunk and would correspond in the cat to a similar 

 rotatory movement effected in the vertical plane. 

 Conversely, the turning mosements of cats in the 

 horizontal plane would correspond to rotatory move- 

 ments of the head in man. Intentional turning of the 

 bodv in man shows the succession of eyes, head and 

 body while passive turning movements produced by 

 vestibular stimuli have an opposite succession of body, 

 head and eyes [Gi^ittich (73), Jung (134)]. In active 



