100 G. STANLEY HALL AND E. M. HARTWELL. gesture-language may persist. If the left brain be hypnotised, as it may be more or less, independently of the right, finer movements, like writing, are difficult with the right hand. Brown- Sequard and Charcot, however, have found that most cases of hemiplegia are also paraplegic ; the apparently intact extremity being much weakened, the leg more than the arm. Pitres found the left extremities less weakened in right (left brain) hemiplegia than the right limb when the left side was affected. In a study of ten cases of right, and thirteen of left hemiplegia with a Duchenne dynamometer, Berger and his pupil, Friedlander, have recently verified these observations, and found a few cases in which greater energy could be developed by the affected than by the intact leg but, instead of finding the loss of power in the sound limb greater in recent cases, could not observe any inflence due to the duration of the case. This duality has often been contrasted both with the medial position of some of the medullary centres and with the apparent unity of thought and the functional simplicity of the soul, which latter postulate, as is well known, inclined Descartes to locate it in the pineal gland. Dr. Wigan, however, did not hesitate to speak of two brains which might carry on two independent trains of thought, but which it was the object of education to make co- work, each as the sentry and security of the other. Scholars are able to think of only one thing at a time, and hard study occupies both brains, so that neither is left to work off its energy by causing dreams. We are made of two beings, he held, and, if the two brains are about balanced, vacillation is certain. In fact, one brain is nearly always superior, and controls the other. One brain may be insane, and, if the stronger one be sound, may be long controlled, and its defect concealed by an effort to hold the " self " together. The power to compel the weaker brain to the will of the stronger marks one of the greatest differences between men, and there are many colloquies between the hemi- spheres. Insane incoherence is like reading a few words from one book and then a few from another on entirely different subjects, with rapid alternations ; a few such duplex trains of thought, Dr. Wigan believes, he has restored to sense by proper disjointing, and rejointing. Dual consciousness, reverie, castle-building, counting steps absent-mindedly, imaginary aggrandisement, supernatural suggestion, another person thinking in the brain, struggles with temptation, characters compounded of bravery and cowardice, hypocrisy and enthusiasm, chess-playing, the half identification with their roles by actors, lucid intervals, the case of lunatics whose illusion is not absolute (who are John Smith or deity, who are kings but strive to conceal it, or who struggle long against morbid or criminal impulses), these all illustrate and are explained by the duality of mind and its organ as incidents in the struggle and alternate supremacy of two rivals which should co-operate as amicably as the Siamese twins. Holland thought
