daughter of philosophy, certainly has some difficulty in making clear its title to a place among the sisterhood of the sciences.

But psychology has had a new birth; and medicine, if not its new mother, may at least be called its grandmother, since it is to the physiologists that the new line of development is principally due. Beginning in a small way early in the last century, progressing slowly for several decades, then spreading out with great rapidity, this new, or physiological, or experimental psychology-though its professors often backslide into the old unregenerate ways, even as physicians, too, often betray a leaning toward philosophical speculation, to little profit-yet on the whole recent psychology has shown a sincere purpose to search for new facts, and to develop adequate empirical methods for establishing them. Many of the results so far achieved are neither startling nor specially illuminating, yet material is gradually being accumulated that deserves the attention of whoever has to deal seriously with the workings of the human mind. Accordingly, we see that the day of applied psychology is beginning, and that, in spite of pessimism in high places, investigators are finding it possible to apply the results and especially the methods of experimental psychology to the solution of important problems in education, law, and even business.

Though isolated from each other, psychology and psychiatry have not been without interest in each other's results; it must be feared, however, that the knowledge each has had of the other has often been indirect and vague. Thus far, it appears that psychiatry has had the worst of the bargain, that she has given much more than she has received in exchange. The clinical observation of mental defects and abnormalities has thrown a great deal of light on normal psychology. The most definite information that we have received from you is perhaps the delimitation of certain mental functions by means of those cases in which the brain defect can also be demonstrated, as in aphasia and psychical blindness and deafness. The order of dissolution of the mental powers in such a disease as paresis is suggestive to us of their order of rank in normal life. Morbid states of exaltation and depression, with the incompetency that attends them, help us to formulate the conditions of efficient intellectual work. Delusions, phobias, fixed ideas-these seem to the psychologist to be

supplied by nature in lieu of some magic microscope which should magnify the scarcely perceptible details of mental life into such proportions that they could not be overlooked. And so one might continue cataloging the indebtedness of psychology to psychiatry, and run up a long list of items of information which you have supplied, and which we, so far as we have known and understood them, have found of value, and oftentimes of very great value, in analyzing the performances of the mind, and in pointing the way to further discovery.

On the other side, alienists have not been neglectful of the teachings of psychology, though it may be feared that they have frequently found them rather barren of practical applications, and even rather lacking in suggestions for the scientific description and explanation of mental abnormalities. Psychology might be a help in furnishing names and modes of expression, but for real insight into the workings of the deranged mind, it has perhaps appeared to offer little that could not be gained by an attentive observer who had never bothered his head with psychological books. This was almost necessarily the case so long as psychology based all its statements on common observation. To get special results special methods are needed. To increase the stock of facts beyond what common observation could reveal, psychology had to develop methods that were finer than those of common observation. This she has done to a considerable extent, and is doing more and more. While she is as yet in no position to point with swelling pride to her achievements, she may fairly claim that she has accomplished enough to be of some service; and may fairly ask to have her stock of goods re-examined by the psychiatrist, in the hope that he will find there something of use to himself. As an illustration of the change wrought by experimental methods, I may mention the application of psychology to certain legal problems. The criminal lawyer has to be a practical psychologist, yet the study of psychological textbooks has not proved of great assistance to him. He knew men from his own observation, though he might not express himself in the technical terms of the psychologists. But some one thought to apply the methods of experimental psychology to such problems as the reliability of the testimony of eye-witnesses, and unearthed such a degree of unreliability as surprised the lawyers. The

results of these and similar experiments that have been made. were such as to demand very careful consideration from the legal profession.

Common observation is not a thoroughly reliable guide. There are, of course, facts so patent as to require no special precautions for their detection. But the further the experimental psychologist carries his researches, the more skeptical he becomes of the value of common views and easily accepted doctrines regarding the mind. The trouble is not indeed wholly one of observation; the tendency to supplement what we can see by what we imagine to be there, to speculate where we cannot prove, is perhaps ineradicable in human nature, and specially in psychology on account of its long-standing association with philosophy. There are current in psychology numerous well-appearing theories which when looked into are found not to rest on experimental observation, but on a few superficial statements of fact, eked out by a vast amount of logical construction. All such are properly subject to suspicion, and the more beautiful and self-consistent the logical construction, the more suspicious they are, because they are so much the less likely to owe their acceptance to agreement with fact. The experimental psychologist holds that we shall never know much about the mind until we take the trouble to find it out, and that the trouble will consist in controlling the conditions under which observations are made and in using sufficiently fine methods of observation.

As an example of a doctrine which owes its currency to superficial observation, and which, nevertheless, has been used extensively in the explanation of mental phenomena, we may take the view that the brain is very liable to fatigue. Common observation seemed to show that fatigue comes on very quickly in mental work, and this apparent fact has done duty in many psychological explanations. "Constant errors" in sense perception, shiftings and fluctuations of attention, changes in the efficiency of mental work, have been regarded as sufficiently accounted for by appealing to mental fatigue. The brain was supposed to fatigue so much more rapidly than the muscles, that what was apparently muscular fatigue has been explained as more probably brain fatigue. It was even suggested that the nervous system, by its capacity for quick fatigue, served to protect the muscles from

overwork, much as a fuse in an electric circuit, by burning out easily, protects the more valuable apparatus in the circuit from excessive currents that would damage them. There was a certain amount of inconclusive experimental observation behind this view, but for the most part it owed its acceptance to the common observation that people, or rather many people, grow tired quickly of mental work, and feel that they must stop. Experimental tests in prolonged mental work have, however, revealed a surprising degree of resistance to fatigue. A series of reaction time tests, continued all day and on into the evening, failed to show any marked decrease in speed. Memory tests continued without break for five solid hours showed a steady improvement throughout. School children have been found as successful in sharp mental tests at the close of school in the afternoon as they were at the opening of school in the morning. College students, so far from being mentally incapacitated by the hard mental labor of a three-hour examination, have actually done better in all sorts of mental tests after the examination than before it. More thorough study of the fatigue of the neuromuscular apparatus has shown that this fatigue is certainly in large part, and perhaps entirely, muscular. If muscular exertion is as far as possible excluded, as when the movements are required to be not forceful, but accurate, they can be repeated hundreds and thousands of times with no pause for rest, and without showing any marked degree of fatigue. In all probability, the central nervous system, like the peripheral nerves, so far from being quickly worked out, is capable of an enormous amount of continued activity without serious loss of functional power. How then are we to explain away the common observation of quick fatigue in brain work? Experiment shows pretty conclusively that this familiar form of fatigue is a sensory or emotional affair, a feeling of fatigue, not a true fatigue in the sense of incapacity. In case of the fatigue that appears early in muscular exertion, at a time when the muscles are still demonstrably in good condition for work, the fatigue is really composed of unpleasant sensations that come in from the active members. The tendency of these sensations is to make us stop the activity that is causing them; but if we resist this tendency, and continue the muscular effort, we find that we are not incapacitated after all; we can

still keep on, almost if not quite as well as before, in spite of the sensations of fatigue, which indeed usually disappear with the further continuance of the muscular activity. Similar remarks apply to the fatigue that is apt to come on early in mental work; it is composed partly of ennui-a mere emotion-partly of tendencies to do something more agreeable to the natural man, partly of sensations of strain arising from the eyes, neck, and various parts of the body, which dislike being held fixed in a cramped position. Let the mental worker resist this medley of incentives to stop work, let him determine to stick to it for a while longer, and he will usually find that his brain is still in good working order, that the feeling of fatigue passes away, and very likely that his best work is done after rather than before the time when his feelings told him he was played out. I have dwelt on the matter of fatigue partly because these results from normal persons may be of some interest to the psychiatrist for comparison with the conditions that obtain in abnormal brains, and partly as an illustration of the value and necessity of experimental methods for determining the real facts, even in the most familiar situations of life.

The main suggestion which as it seems to me experimental psychology has to offer to psychiatry is contained in just this demonstration of the insufficiency of common observation and the treacherous nature of logical schemes of mental function which rest only on common observation for their empirical basis. If this is true in normal psychology, it appears almost certain that it will prove true for abnormal psychology as well. The psychiatrist is to be sure concerned primarily with divergencies from the normal, many of which are so obtrusive as to require no special devices for their detection. That the paranoiac is deluded, the maniac excited, the hysteric unstable and suggestible, that certain patients suffer from hallucinations, or from amnesia, or from confusion, the common methods of observation sufficiently show. Moreover experimental methods cannot supplant and make unnecessary the methods of clinical observation that have gradually been developed in the experience of alienists. Just so, in the general practice of medicine, the thermometer, the test-tube and the microscope have not supplanted the less special methods. of clinical observation. But just as recent progress in medicine