Page:Principles of Psychology (1890) v1.djvu/95

75 FUNCTIONS OF THE BRAIN. 75 70, which is said to have been kept alive for fifty-one days after both hemispheres had been removed by a series of ablations and the corpora striata and thalami had softened away, shows hov/ much the mid-brain centres and the cord can do even in the canine species. Taken together, the number of reactions shown to exist in the lower centres by these observations make out a pretty good case for the Mey- nert scheme, as applied to these lower animals. That scheme demands hemispheres which shall be mere supple- ments or organs of repetition, and in the light of these observations they obviouslj^ are so to a great extent. But the Meynert scheme also demands that the reactions of the lower centres shall all be native, and we are not absolutely sure that some of those which we have been considering may not have been acquired after the injury ; and it further- more demands that they should be machine-like, whereas the expression of some of them makes us doubt whether they may not be guided by an intelligence of low degree. Even in the lower animals, then, there is reason to soften down that opposition between the hemispheres and the lower centres which the scheme demands. The hemi- spheres may, it is true, only supplement the lower centres, but the latter resemble the former in nature and have some small amount at least of ' spontaneity ' and choice. But when we come to monkeys and man the scheme well-nigh breaks down altogether; for we find that the hemispheres do not simply repeat voluntarily actions which the lower centres perform as machines. There are many functions which the lower centres cannot by themselves perform at all. When the motor cortex is injured in a man or a monkey genuine paralysis ensues, which in man is incurable, and almost or quite equally so in the ape. Dr. Seguin knew a man with hemi-blindness, from cortical injury, which had persisted unaltered for twenty-three years. 'Traumatic inhibition' cannot possibly account for this. The blindness must have been an ' Ausfallser- scheinung,' due to the loss of vision's essential organ. It would seem, then, that in these higher creatures the lower centres must be less adequate than they are farther down in the zoological scale ; and that even for certain elementary