912 



THE 



'RVE SYSTEM 



true optic path: it is a, separate flascicular representation of the infracommissure 

 of Gudden. composed of fibres forming a reciprocal bond of union fcommissural) 

 between the internal geniculate / bodies of the two sides and coursing through the 

 chiasm (Fig. 668). The lateral root of the optic tract is the true visual path, com- 

 posed of (a) the uncrossed fibres from the lateral half of the retina of the same side 

 and (b) the crossed fibres from the mesal half of the retina of the opposite side. 

 The fibres of the lateral root are distributed to the primary or lower optic centres 

 as follows: (1) Most fibres end in the external geniculate body; (2) a less number 

 end in the pulvinar; (3) the remainder end in the nucleus of the superior quadri- 

 geminal body. 



MEDIAL GENICU- 

 LATE BODY 

 SUPERIOR QUADRI- 

 GEMINAL BODY 



OCCIPITAL CORTEX 



FIG. 668. Scheme showing central connections of the optic nerve and optic tract. 



The lateral fffirnculate body and pulvinar are ganglionic way-stations or inter- 

 nodes in which visual impulse are reflected, in large part to the visual cortex 

 in the occipital lobe: the superior quadrigeminal body, on the other hand, plays 

 no part in the conduction of impulses perceived as ligh/or color; it presides rather 

 over the eve-muscle reflexes to visual 1 stimuli, and in its/ turn is under the dominion 

 of the higher cortical centre. Reflex impulses are sen/ to the oblongata and spinal 

 centres along axones entering into the formation of the/medial longitudinal bundle. 



1 And auditory stimuli as well (see p. *99). 



