1, Internal carotid artery, divided at the opening of the cavernous sinus; 2, anterior cerebral artery; 3, middle cerebral artery and Sylvian artery; 4, choroid artery; 5, anterior communicating artery; 6, posterior communicating artery; 7, posterior cerebral artery, with (7) its anterior, (7") its middle, and (7") its posterior branches; 8, basilar artery; 9, superior cerebellar artery; 10, inferior and anterior cerebellar arteries; 11, bulbar arteries; 12, vertebral arteries; 13, inferior and posterior cerebellar arteries; 14, anterior spinal artery; a, anterior extremity of inter-hemispherical fissure; b, its posterior extremity; c, olfactive bulbs; d, optic commissure; e, pons; f, bulb; g, cerebellum. The left hemisphere of cerebellum and right temporo-sphenoidal lobe have been removed.

and in the cortex or investing gray matter we find the seat of that form of nervous action which is the direct output of cellular function. In some places are well-determined areas whose special office is to originate definite motor impulses. Thanks to Hitzig, Fritsch, Ferrier, and a host of other observers, we know that localized irritation of these will be followed by muscular contractions in distal parts, and that these are of a uniform character, as can be repeatedly proved. We know that posteriorly in the occipital lobes are located centers for vision; that above in the parietal region is what is known as the angular gyrus, a center for the coördination of symbols that play a part in audition; that anteriorly on the left side of the brain, at the foot of the third frontal convolution, is a center for speech, and that when destroyed the condition known as aphasia is a result; that at the base of the brain anteriorly is a center for smell. These, as well as many others, have been located by experiment and proved to exist by the results of disease.

What the exact location of the apparatus of mind is has always been a matter of active dispute, although the great mass of testimony goes to show that it is the fore-brain which is concerned. In the light of experiment and clinical observation this theory seems open to some question, and the views of Hughlings-Jackson and Exner are less conservative and more reasonable. I am therefore inclined to agree with them that no one part of the gray matter is alone concerned, but rather that mental action is the result of general and complex function. Figs. 2, 3, 4, 5, 6, 7, 8, 9, and 10, from Testut's admirable treatise (Traité d'Anatomie Humaine, etc., t. 2, Paris, 1893), will enable the reader to more readily recognize the intricate system of communicatory or associative fibers in the brain itself, as well as those which pass centrifugally. The sensory organs and tracts that are engaged in the production of mind are extensive and intricate, and not only connect the concept, propositionizing, auditory, visual, and other sensory and motor centers which may be almost adjacent, but those as well which are more remote, and others form important tracts which are direct or commissural. Figs. 2, 3, 4, 5, diagrammatically illustrate the course of these fibers. Figs. 6, 7, 8, 9, 10, indicate the general connection of these with parts of the brain in which special functions are located; Fig. 6 showing the entire lateral cortical surface of one hemisphere, with its function-zones mapped out and either represented in color or by limiting lines, and Figs. 7, 8, 9, and 10, the association systems of the fore-brain. Fig. 11 shows the important basal arterial circulation of the brain, which is often subject to obstructive changes or other disease, especially in those forms of dementia consecutive to thrombosis, embolism, or rupture from any other cause, the left middle cerebral artery being that most often involved.

Kirchhoff (Handbook of Insanity, p. 9) formulates the status of knowledge of localization regarding the deductions to be drawn from disease or non-development of the brain. He calls attention to the fact that :

1. "The interruption of certain systems of fibers leading from the cerebrum to the cerebellum gives rise to distinct slowness and difficulty of the mental functions.

2. "The optic thalamus seems to possess more intimate relation to the higher mental functions than does the corpus striatum, inasmuch as the former alone undergoes atrophy in congenital absence of the cerebral hemispheres.

3. "The disturbance in the intellectual development of individuals in whom the corpus callosum is absent is very small, indicating that the higher mental processes are not dependent upon the frontal brain alone; indeed, in these cases the occipital lobes are mainly atrophied.

4. "If the brain is imperfectly developed as a whole, as in some idiots, there can be no question of localization, nor is any further conclusion warranted from irregular development in the cortical layers, unless it is circumscribed."

In illustration of this he alludes to the discovery of only narrow pyramidal cells in the frontal lobes of a few idiots, which were so irregularly distributed that it was almost impossible to distinguish the layers. Here the imperfect mental development may be attributed to the imperfect development of the frontal cortex.

There appear to be no means of determining the seat of memory, but judging from the complex processes which operate in the formation of concepts, as well as their diverse nature, it is probable that they are stored up in no particular locality; in fact, the pathology of dementia and its morbid anatomy presume a progressive and general destructive change.

MENTAL ELEMENTS-NORMAL AND DISEASED.

Any extended consideration of physiological psychology in a book of this kind would be out of place, but it will suffice to state that the divisions of mind are three in number: feeling, which includes sensibility and emotion; thinking, which implies intellection or thought; and volition, which is a result of the exercise of the first two. These may be still further amplified and subdivided. In the older definitions of mind it was the custom to speak of judgment, reason, and memory, but, after all, these may be better included under the head of "thinking."

In the study of the normal as well as of the diseased mind we are to consider perception, which implies the recognition and appreciation of the relations of sensation and the agencies which affect the same. This means the recognition of the part played by the organs of special sense -the afferent nerves of conduction, the existence of groups of cells or nerve centers which receive the impressions from without, and the more important condition of consciousness. The kind of intelligence which is necessary for the mensuration of the form and physical attributes of objects must be taken into account, especially when we come to consider the formation of hallucinations and illusions. When a perception has been recognized and remembered, it becomes a concept or idea; and when comparison is made and the process of reasoning takes place, a judgment is arrived at.

One of the most important mental faculties is that of memory, which enables the individual to retain and store up impressions, and which really forms the basis of the most important forms of higher mental activity. Memory may be said to be of two kinds-that which consists in the retention of perceptions or external impressions, and that which concerns the acknowledged recognition of self and the inner condition (organic memory). Sensations of a personal kind are recognized and remembered, and form the basis of self-appreciation. This latter form of memory, when affected, results in the change of the ego which is so

marked in some hallucinatory insanities. The grouping of concepts or ideas, and their association, constitutes reasoning and judgment, and precedes volition, which may be the demonstrative active expression of their conclusion. The degree of this manifestation of course varies very much with the complexity and the extent of the mental operations which are behind it; and it differs from reflex action in the fact that the active demonstration is not governed by thought in the latter, but is the result of a lively external impression, which is spinal in character, and the motor expression may or may not be attended by unconscious cerebration.

The simplest form of reflex action may be illustrated by the rapid withdrawal of the finger from a hot surface, which produces actual physical pain, the cause or degree of which is not weighed or estimated by the mind, and the act itself is also too rapid to be a volitional one. Then, again, there are so-called instinctive reflex acts, where previous associations and experiences enter into the causation of particular muscular contraction, and where no apparent conscious appreciation exists. The importance of the volitional act is, of course, gauged largely by the participation of reason and judgment, as well as the concurrence of affective feeling; and we are presented in health and disease with many gradations in the acts of will which begin as impulses and reach the dignity of elaborate exercise of force after comparison, judgment, and discrimination have been operating. The capacity for inhibition, and, on the other hand, the influence of emotion and the absence of self-control, are to be considered.

In the study of those conditions which suggest mental disease we are, of course, to ascertain, if possible, not only the previous life of the individual, but his environment and such causes as may have resulted in the mental degeneration. We are also to compare his mental expressions and conduct with that of others in the community in which he may be living, to consider his training and education, and to go back, if possible, into the remote past, to discover what influence, if any, has been exerted upon his development as a result of the willful faults or involuntary misfortunes of his progenitors. Mental disease is not, as a rule, of sudden origin. There is nearly always some predisposition or some long-existing cause, and in a very great many cases the process of mental dissolution is a slow one and the departure from mental health is prolonged. This should be borne in mind, especially in the consideration of cases which form the subject of legal inquiry; but the popular idea of insanity implies all sorts of possibilities and improbabilities which do not stand the test of clinical experience.

Special Indications of Mental Weakness. '

Among the important evidences of mental deterioration are Hallucinations; Illusions and Delusions; Insistent and Imperative Concepts; Loss of Memory (both external and organic); Inharmonious Exercise of Ideation or Reasoning Power; Emotional Disturbance and Volitional Diminution or Exaggeration; Physical Changes.

HALLUCINATIONS.

An hallucination is a false perception, and in this respect differs from an illusion, by reason of the fact that the error leading to the creation of the latter consists in the distortion of an objective thing. Hallucinations are of three kinds :

First. Those due to a defect of the peripheral perceptive organ, or of the afferent nerves and centripetal fibers.

Second. The form which includes examples of disturbance of certain central organs.

Third. Where the disorder is chiefly confined to limited cortical areas. It has been held by some authors that it is possible to have hallucinations without any cerebral participation, or, in other words, any mental aberration, the organs of special sense themselves possessing a certain local memory. This seems to me to be a meretricious distinction and one wholly speculative, for the reason that it is impossible to have an hallucination without a previously formed concept, no matter how ancient. Persons who become blind after a time may have visual hallucinations, but those congenitally blind can, of course, have nothing of the kind, as no image has ever been projected upon the sensorium.

It is important to consider hallucinations with regard to their pathogeny: first, in connection with the organs of special sense themselves; and second, where they are centrally originated, as a result of an irritation and stimulus of certain brain tracts where concepts have been stored up.

The simplest form of hallucination is that due to some local irritation or disease of one of the perceptive organs, and the false images need not necessarily be insane; in fact, a variety of spurious sensory images, without objective basis, may be recognized by the individual as the result of disease or temporary disturbances of the cerebral circulation, he being able to appreciate their source, and it is only when the higher powers of the mind are so diseased that comparison and judgment fail to act as correctives, that the mental integrity of the individual is questioned. All varieties of sensory impression are likely to be perverted by causes which it is not necessary to mention here, except in a general way; but we may consider the numerous factors that may pervert the innervation of the important organs which serve to keep us in relation with the outside world. It is not difficult to explain by purely physical agencies many startling varieties of disturbed special sensation.

Hallucinations are divided into visual, auditory, olfactive, and cutaneous. Visual hallucinations are largely dependent upon retinal phenomena, and are often connected with ischemia or disturbed circulation at the back of the eye. The pulsation of the central artery or variations in the retinal light may give rise to rings or disks of light, dark spots, flashes, stars, or other scintilla, which may or not be used by a diseased brain as a basis for an elaborate morbid concept association.

What other expansion there is of the mechanism which results in the misinterpretation of simple distal variations, I am unable to say. It would appear, however, that a very indifferent form of peripheral stimulation will often start a train of disorderly thought at a time when inhibition is not exerted. During the condition of sleep, when the upper