The central path of the light reflex via the sympathetic nerve in the cat was studied by observing reflex inhibition of the activity in the long ciliary nerve after various combined lesions of the brain stem and optic tract. From the results a possible schema was induced.
The inhibitory path from the unilateral eye to the cilio-spinal centers entered into the midbrain through the bilateral optic tracts after a partial decussation in the optic chiasma. From there a part of them descended the midbrain, pons and medulla oblongata on each side, while the other descended the contralateral brain stem after a partial decussation both in the posterior commissure and ventral to the Sylvian aqueduct. Furthermore, this descending path reached the bilateral cilio-spinal centers after forming the 3rd partial decussation in the spinal cord. In the medulla oblongata this inhibitory path occupied a position in the ventral reticular formation.
