The Functions of the Brain

fishes and birds, and from the anterior tubercles of the corpora quadrigemina in the lower orders of mammals, and the similar, though less apparent, connection of the optic tracts in the monkey and man with the corpora quadrigemina, through the medium of the corpora geniculata and their brachia or arms, would almost, without experimental proof, indicate that these ganglia have an important relation to vision. But it would by no means follow that these ganglia are the centres of vision, even though it should be found that destruction of them produces blindness. Destruction of the optic lobes would naturally break the continuity of the optic tracts, and so cut off the eyes from the perceptive centres. That these ganglia are not the centres of consciousness of visual impressions, or sense of sight, has already been indicated in a former chapter (§ 21), and experimental demonstration of this fact will be furnished subsequently (§ 65). This is further borne out by the anatomical investigations of Gratiolet and Meynert, which have led them to the conclusion that the optic tracts likewise enter into relations with the optic thalami, and with radiating fibres, which proceed to the lateral and posterior regions of the cerebral hemispheres. . The facts of anatomy and those of physiological experiment mutually support the view that the corpora quadrigemina, though not the centres of conscious vision, are centres of coordination of retina impressions with special mo...