400 



PHYSIOLOGY 



CHAP. 



or other gyrus angularis still produces synergic movements of 

 the eyes. On the other hand, these cannot be obtained when 

 the brain-stem has been divided between the aqueduct and the 

 region of the oculomotor nuclei, showing that the fibres which 

 unite these nuclei with the gyrus angularis undergo complete 

 decussation in the median line below the Sylvian aqueduct. 



Fig. 187, published by Bernheimer (1902), is a diagram of 

 the paths which subserve the associated lateral or convergent 



eye 



Right eye 



R. est. 



Oculomotor/ nuc. 

 Centre of /R. ink 



Visual area 



FIG. 187.- Diagram of nerve paths concerned in lateral and convergent movements of both eyes. 



(Bernheimer.) 



movements of the eyes. When both eyes are voluntarily turned 

 to the right, the motor impulse starts from the region of the left 

 angular gyrus, travels along paths 1, 2, 3, and produces con- 

 traction of the external rectus of the right eye, simultaneously 

 travelling along paths 1, 2, 4, 5 contraction of the internal rectus 

 of the le/t eye. If the eyes converge voluntarily, the impulse 

 starting from the angular gyrus of one or both hemispheres 

 travels along paths 1, 2, 4, 5 and 1, 2, 4, 6, and produces con- 

 traction of the internal recti of both eyes. 



It is easy to understand that, after unilateral destruction of 

 the gyrus angularis or of paths 1, there must be conjugate 



