66 PSYCHOLOGY. tor's hand, and yet be proved by circumstantial evidence to exist all the while in a split-off condition, quite as ' ejective ' * to the rest of the subject's mind as that mind is to the mind of the bystanders. t The lower centres themselves may conceivably all the while have a split-off consciousness of their own, similarly ejective to the cortex-consciousness ; but whether they have it or not can never be known from merely introspective evidence. Meanwhile the fact that occipital destruction in man may cause a blindness which is apparently absolute (no feeling remaining either of light or dark over one half of the field of view), would lead us to suppose that if our lower optical centres, the corpora quadrigemina, and thalami, do have any consciousness, it is at all events a consciousness which does not mix with that which accompanies the cortical activities, and which has nothing to do with our personal Self. In lower animals this may not be so much the case. The traces of sight found (supra, p. 46) in dogs and monkeys whose occip- ital lobes were entirely destroyed, may possibly have been due to the fact that the lower centres of these animals saw, and that what they saw was not ejective but objective to the remaining cortex, i.e. it formed part of one and the same inner world with the things which that cortex per- ceived. It may be, however, that the phenomena were due to the fact that in these animals the cortical ' centres ' for vision reach outside of the occipital zone, and that destruc- tion of the latter fails to remove them as completely as in man. This, as we know, is the opinion of the experiment- ers themselves. For practical purposes, nevertheless, and limiting the meaning of the word consciousness to the per- sonal self of the individual, we can pretty confidently answer the question prefixed to this paragraph by saying that the cortex is the sole organ of consciousness in man.^ If there
- For this word, see T. K. Clifford's Lectures and Essays (1879), vol. ii.
p. 72. f See below, Chapter VIII. X Cf. Ferrier's Functions, pp. 120, 147, 414. See also Vulpian: Le9on3 sur la Physiol, du Syst. Nerveux, p. 548; Luciani u. Seppili, op. cit. pp. 404-5; H. Maudsley: Physiology of Mind (1876), pp. 138 ff., 197 ff., and 241 ff . In G. H. Lewes's Physical Basis of Mind, Problem IV: ' The Reflex Theory,' a very full history of the question is given.
