It will be remembered that for convenience' sake I have discussed the dynamogenic effect of suggestion first upon the external senses, then upon the internal sensibility,--the mind's eye, the mind's ear, and the imagination generally;--and now I am turning to similar effects exercised upon that central power which reasons upon the ideas and images which external and internal senses supply, which chooses between them, and which reacts according to its choice. These are "highest-level centres," which I began by saying that the hypnotist could rarely hope to reach;--since those spontaneous somnambulisms which the hypnotic trance imitates and develops do so seldom reach them. We have, however, already found a good deal of intelligence of a certain kind in hypnotic phenomena; what we do here is to pass from one stage to another and higher stage of consciousness of intelligent action. To explain this statement, let us dwell for a moment upon the degree of intelligence which is sometimes displayed in those modifications of the organism which suggestion effects. Take, for instance, the formation of a cruciform blister, as recorded by Dr. Biggs, of Lima.[84] In this experiment the hypnotised subject was told that a red cross would appear on her chest every Friday during a period of four months. For the carrying out of this suggestion an unusual combination of capacities was needed;--the capacity of directing physiological changes in a new way, and also, and combined therewith, the capacity of recognising and imitating an abstract, arbitrary, non-physiological idea, such as that of _cruciformity_. All this, in my view, is the expression of _subliminal_ control over the organism--more potent and profound than _supraliminal_, and exercised neither blindly nor wisely, but with intelligent caprice. Bearing this in mind as we go on to suggestions more directly affecting central faculty, in which _highest-level_ centres begin to be involved, we need not be surprised to find an intermediate stage in which high faculties are used in obedience to suggestion, for purely capricious ends. I speak of _calculations_ subliminally performed in the carrying out of post-hypnotic suggestions. These suggestions _à échéance_--commands, given in the trance, to do something under certain contingent circumstances, or after a certain time has elapsed--form a very convenient mode of testing the amount of mentation which can be started and carried out without the intervention of the supraliminal consciousness. Experiments have been made in this direction by three men especially who have in recent times done some of the best work on the psychological side of hypnotism, namely, Edmund Gurney, Delbœuf, and Milne Bramwell.