movement. Light from the window, and sounds in the house produce numerous currents streaming up afferent fibres, quickly followed by numerous motor unions among nerve-cells, and visible movements as the child wakes up. In the school-room before lessons, we see activity in the brain, numerous flashes of blue light shew the many unions occurring and dissolving among the cells, while the efferent currents pass away to the muscles. Then as he takes his place in class, and the teacher calls for attention, we see him still and quiet, no efferent currents pass to the muscles, still blue light flashes about the cells of the brain as he thinks over the lesson. When he sits and looks at his book unions are being formed in his brain; when told to say his lessons, currents pass from those unions to the muscles which produce vocalization. In explaining the modes of action of nerve-centres, the Lecturer used a Mechanical Diagram as above, representing a certain area of the brain. The circles represent brain centres; when a centre is presented as black it is sending out force to muscles, and producing visible movement in the body as expressed by elevation of signals at the side, the full action of A causes elevation of signal a etc.; centres C, G are supposed to be active but not to be sending nervecurrents to muscles. Centres B, D, E are not acting. Natural Orders of plants. CHAPTER III. FUNCTION OF BRAIN DISPLAYING MIND ACTION. Modes of NATURAL phenomena may be described in various description. ways according to the special purpose in hand, and the object which it is sought to attain. This may be illustrated by the history of the science of botany. In the early period of this science, the object in view was to identify, remember, and name all vegetables. The principal characters used in defining the Natural Orders are based upon the number of parts of the flower, their mutual form, position, cohesion, adhesion etc., i.e. upon structural characters. It is not convenient to use the colours of flowers as the basis of classification. In the early studies of botany the great object in view was to advance the classification and naming of plants, and for this purpose points of structure were noted with the greatest advantage and convenience, the character colour being neglected or considered as quite subordinate in importance to structure. When classes of plants had been arranged, and the individual species described according to structure, and named, it became easier to study the distribution and the properties of plants, and thus new knowledge was gained. Such descriptions are clear, and very useful for the purpose of helping us to determine the order and species of a plant. If the purpose of the naturalists' to colour. studies be to obtain knowledge as to the relations of Flowers insects to plant life, then the descriptions which served classed as for the purposes of botanical classification will not suffice. With the change of purpose of study, various other characteristics of the flowers must be observed; colour now becomes of prominent importance. Flowers may be classed according to their colours, and the special insects visiting the red, blue, and white flowers respectively may be noted thus we gain a new kind of knowledge. : Let us now turn to the purpose of this Lecture,—the Psychosis study of the brain as an organ producing the manifesta- or mental action of tions of mind. The term Psychosis is here used to brain. express the physical processes occurring in the brain which are connected with the action of mind. I have found it convenient to omit from the definitions and descriptions here used, all terms implying subjective conditions which are incapable of direct observation by our senses. I have adopted this plan for several reasons, among others, in the desire to correlate the facts of mental action with other processes of nature, and to trace the effects of the forces around us, which, acting upon the body and the brain, produce aptness for the display of mind. mental action. The study of mental action thus becomes a study of Physicophysical facts, as is the study of any other subject in physiology, or the study of the phenomena of light, electricity, or sound. The electrician observed facts, and framed hypotheses to afford explanation of them, hence, we hear his views as to induced currents, Ampère's currents, etc.. In studying light the amplitude of waves of ether has been measured. In these branches of science hypothesis has correlated facts, aided understanding, and given definite thoughts which have led to further observation and the acquisition of much useful knowledge. Mental action will be studied by methods. Mental action studied like similar to those used in the case of motion and growth. It has been shewn that all expression of mental action motion and is by movement and the results of movement; it will growth. then be anticipated that the methods used in the analysis of movements may be applied to the analysis of mental acts, and that the forces which control and regulate movements also appear to control and regulate action in the brain displaying mind. mental action. I have demonstrated in my Lectures on the Anatomy of Movement, that the actions of man consist of combinations and series of movements, and that they are usually determined by some stimulus from without. It is also there shewn that similar actions, or combinations and series of movements, may occur in different men under similar stimulation. Movement To understand the theory of psychosis which I am expressing about to advance, it is essential to remember what was said in the preceding lecture about double action in nerve-centres and delayed expression. Movements expressing the action of mind, like other nerve-muscular acts, imply local minute change, in the nerve-centres, and currents passing from them to the muscles, the former, or the act of getting the centres ready for action, must always precede the movement: it is this formation for action in the centres, or getting ready for action that I believe to represent the physical act of thought. We cannot define a thought, that is a metaphysical term, we can describe the expression of thought by movement, and may infer the time of the act in the brain centres preceding it. I can only know the thought of another man by its expression in movement, or the results of his movements, the thought precedes its expression. The nerve-mechanism for the thought is probably a part of the mechanism for its expression by movement. Studying processes of growth in living beings, and Growth movements in man, teaches us much as to action in the movement. Thought. brain-observation of the motor action of the brain enables us to make generalisations as to the processes occurring in its parts or nerve-centres. From studying the expression of mind, we shall argue as to the action occurring in the brain which corresponds to the physical action called "thought," which is known to us by subsequent expression in movements. While studying processes of growth in many living things, and movements in man, especially movements indicating mental action, and observing the antecedents and sequents of such acts, I was led to frame a working hypothesis as to the physical action in the brain corresponding to a mental act. action. The hypothesis is "That every mental action (act Hypothesis of psychosis), as every motor action, depends upon the asto mental formation and action of a certain combination of the nerve-cells." The sum of the phenomena of mind may be considered as a mass of separate mental acts. It is very generally admitted that in some way the organisation and functions of the brain are concerned in displaying mind. It is assumed here, that a mental act is not the act of one mass of brain which does nothing but produce that one thought, but the outcome of the particular set of cells which happen at the moment to act together, the union of cells for such act being temporary though capable of recurring. It has been shewn that one group of cells acting together produces one particular movement, and it is believed that similarly one group of cells can produce one particular act of mind; the particular thought thus depends upon the particular group of cells acting. It is also believed that groups of cells can be |