The brain in man and in all the higher animals is a very complicated organ made up of a number of different parts. To simplify the description as much as possible we shall omit all account of smaller subdivisions and speak only of the most important parts. These are three in number, named the cerebrum, the cerebellum, and the brain stem. Their location with reference to one another is shown herewith.
As the figure shows, the cerebrum is the main part of the brain. It in fact is the part we ordinarily think of, when we have the brain in mind. The brain stem is really the upper extension of the spinal cord within the head. It is a very important part of the brain, because all the nerve pathways in from the sense organs, and from the brain out to the muscles, pass through it. Besides that it has some activities of its own, which will be described a little later. The cerebellum is a subdivision of the brain which plays a very important part, but is not concerned in those complicated nervous actions which make up our mental processes. All these are conducted wholly in the cerebrum. In fact, this section of the brain is the only part which has the ability to stop the progress of nervous disturbances; the property of memory, which was described a moment ago, is found only in the cerebrum. Since the cerebrum is the seat of memory and of our mental life in general, it is both the most interesting and the most important part of the whole body, and a very large amount of study has been given to it. Many years ago attempts were made to show that the brain is subdivided into a number of parts, each of which has control over certain mental characteristics. Nothing very important came of these attempts, although they gave rise to the false science of phrenology, which has been widely exploited by fakers. Notwithstanding the failure of these early attempts at locating particular mental activities in particular parts of the brain, recent studies have shown that there is something of the sort, although it is not at all what the phrenology charts would indicate. It has been shown, however, that the various sense organs do make connections with particular parts of the cerebrum. Comparing the pathways over which the nervous disturbances pass to railroad tracks these places in the brain are often spoken of as the “arrival platforms” of the various senses. Thus the arrival platform for the sense of
