indigestion, physical health and blood circulation, everything, influence our mental make-up. In the same way it is the laboratory experiment which shows by the subtlest means that every mental state produces bodily effects where we ordinarily ignore them. As soon as we apply the equipment of the psychological workshop, it is easy to show that even the slightest feeling may have its influence on the pulse and the respiration, on the blood circulation and on the glands; or, that our thoughts give impulse to our muscles and move our organs when we ourselves are entirely unaware of it. Again we may turn in another direction. Pathology shows us how every physical disablement of the brain is accompanied by mental processes. If the blood supply to the brain is cut off, we faint; a blow on the head may wipe out the memory of the preceding hours, and a hemorrhage in the brain, the bursting of a blood vessel which destroys groups of brain cells, produces serious defects in the mental content. A tumor in the brain may completely change the personality; the bodily disease of certain convolutions in the brain brings with it the loss of the power of speech; paralysis of the brain dissolves the whole mental personality. Physical inhibition in the growth of the brain involves, on the mental side, feeble-mindedness and idiocy. Of course, all this is not sufficient to bring out a definite parallelism between special mental functions and special physical processes, as the phenomena are extremely complex. If a patient who has suffered from a mental disturbance dies, and his brain is examined, there is no simple correlation before us. It may be difficult to diagnose exactly the mental symptoms. If we have heard that the man was unable to read, we do not know from that what really happened in his brain. He may not have read because he did not see the words, or because the letters were confusing, or because he had lost memory for the meaning, or because he had lost the impulse to speak the words, or because he felt unable to turn his attention, or because the impulse to read aloud was not carried out by his organism, or because an inner voice told him that it is a sin to read, or for many similar reasons; and yet each one represents psychologically an entirely different situation. On the other hand, on the physical side, the destruction is probably not confined to one particular spot. Complications have crept over to other places or the disturbance in one part works as inhibitory influence on other brain parts, or a tumor may press on a far-removed part, or the disturbance may be one which cannot be examined with our present microscopic means. In short, we have always a complex mental situation and a complex physical one, and to find definite correlations may be possible only by the comparison of very many cases.