4 8 



ATLAS OF NERVE CELLS 



cortex, is necessary to put 

 in action the coordinating 

 visual apparatus. Hence 

 the double tract established 

 anatomically is a necessity of 

 physiology. But a mech- 

 anism is also necessary 

 to correlate the sensory im- 

 pressions with the motor 

 nuclei of the ocular muscles. 

 This is found in the cells 

 lying in the superficial and 

 deep gray matter of the 

 corpora quadrigemina, among 

 the brushes and cells already 

 described, which send their 

 neuraxons downward to the 

 III., IV., and VI. nerve 

 nuclei, reaching the latter 

 through the posterior longi- 

 tudinal bundle. These con- 

 nections are shown in the 

 diagram, Fig. 8. 



FIG. 8. 

 FIG. 8. Diagram of the corpora quadrigemina anterior, CQA, showing their connections. 



On the right of the figure the superficial and deep masses of gray matter are shown, pulv, pulvinar of the optic thalamus. /, posterior 

 nucleus of the optic thalamus lying between the corpus geniculatum externum, fge, and the corpus geniculatum internum, fgi. fC, internal 

 capsule. /", fillet. KN, red nucleus of the tegmentum. FED, peduncle of the cerebrum. sn, substantia nigra. OT, optic tract. X, optic 

 chiasm. //, optic nerve. /, 2, fibres from the retina to the pulvinar of the optic thalamus. /, centripetal. .?, centrifugal. 7 and 8, fibres between 

 the optic thalamus and the occipital cortex, 3 and 4, fibres between the retina and the corpus geniculatum externum. 9 and 10, corresponding 

 fibres to the occipital cortex, j and 6, fibres between the retina and the corpus quadrigeminum anterior. // and 12, corresponding fibres to the 

 occipital cortex. For the sake of distinctness the decussating optic fibres only are traced. 13, cell of the superficial gray matter of the CQA sending 

 fibre to the nucleus of the third nerve (/6). 14, cell of the deep gray of CQA sending fibre to third nerve nucleus, rj, cell of the deep gray of 

 CQA sending fibre into the fillet. 77, fibre from the red nucleus terminating about 14. :8, fibre from the fillet terminating about 13. OL, occipi- 

 tal lobe of the brain, with its cortex, containing both cells and terminal brushes of the visual tract. 



