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has not proceeded to the point of overthrowing mental equilibrium. (3) The loss of brain also that has frequently attended on accidents, when a comparison is made between previous and subsequent mental states, does not show any exact equivalence between cerebral and mental activity, nor that the first, is in reference to the second, a measurable force, calling, in every variation, for a measurable correspondence. The brain may be materially reduced even in bulk with immaterial or vacillating results. (4) Its entire automatic action, as well as organic action, proceeds also, with little or no trace on mental states.

States of brain at all times affect and at times control states of mind. (1) The general dependence of mental power on the size, form, quality of the cerebrum shows this functional connection. None can doubt that mental power, in its manifestation, is proportioned to the vigor of nervous action. The condition of the physical instrument is, in a large measure, that of the mental agent. This is a fact of daily observation. (2) Vivisection puts this truth beyond question. Though mental powers do not disappear in definite order and degree with specific portions of the cerebrum, they are disturbed by its injury, and lost by its removal. (3) Diseases of the brain complete the proof. Insanity, partial hallucinations in a great variety of forms, are the constant accompaniments of cerebral disturbance. Not only does such disease diminish mental power, it strangely modifies that which remains. The thoughts seem to be the sport of abnormal, physical conditions. If the mind struggles occasionally for self-possession, it is soon overwhelmed again, and floated on by the current. We must, therefore, grant that, at least in some instances, physical states seems to be the efficient, determining causes of mental ones; though even in these cases the final result combines the two series of forces, physical and mental.