194 PHYSIOLOGY OF CENTRAL NERVOUS SYSTEM. 



this course of the optic fibers is given in the accompanying diagram 

 (Fig. 87). According to this schema, the general relations of each 

 occipital lobe to the retinas of the two eyes is such that the right 

 occipital cortex represents the cortical center for the two right 

 halves of the retinas, while the left occipital lobe is the center for 

 the two left halves of each retina, a relation that agrees completely 

 with the results of experimental physiology and clinical studies. 

 In addition to the fibers described, which may be regarded as the 



Occipital lobe. 



\ 



Optic radiation. 

 Superior colliculus. 



Lateral or external geniculate. 

 Optic thalamus. 



Optic tract. 



Optic chiasm. 

 Optic nerve. 

 Retina. 



Fig. 87. Diagram to indicate the general course of the fibers of the optic nerves and the 

 bilateral connection between cortex and retina. 



visual fibers proper, there are other fibers in the optic tracts and 

 optic nerves whose physiological value is not entirely clear. The 

 fibers of this kind that have been described are: (1) Posterior or 

 Gudden's commissure. Fibers that pass from one optic tract to 

 the other along the posterior border of the chiasma. These fibers 

 form a commissural band connecting the two internal (or median) 

 geniculate bodies, and possibly also the inferior colliculi. It 

 seems probable that they belong to the central auditory path 



