Besides, all the parts of the organism are co-ordinated, and there are wonderful checks and counterchecks which show that animals are much more than colonies of cells fortuitously growing together and habituated to such common life by many generations of heredity and environment and training. In a word, the old vitalistic principle has become popular once more and even great physiologists have insisted that there is a principle of life which guides and controls and co-ordinates the different portions of the body. Especially does this seem to be true of the brain. We have here an intensely complex machine, composed literally of billions of parts which work together, and in doing so accomplish wonderful results. Of the existence of this machine, much more of the great intricacy of its parts and mechanism, we are quite unconscious. We learn to use it in very early years with an assurance and a perfection that is amazing, considering how complex it is. The less we think about it and its workings, the better does it work and the less disturbance of function is there in its accomplishment. [Illustration: Fig. 21.--SECTION THROUGH THE CORTEX OF THE GYRUS OCCIPITALIS SUPERIOR. (Hammarberg. Barker.)] If a vitalistic principle were needed to enable us to understand the workings of the ordinary body cells, how much more is it required for the workings of brain cells. There is something behind that guides and rules the brain, and through which it accomplishes its work. It is this that brings about an unconscious cerebration accomplishing intellectual results for us even when the brain machine itself is at rest as when asleep, or fails, for some reason, to be in readiness to take up the work that we demand of it. It is this vital principle that coordinates the movements of brain cells which represent {133} the physical processes underlying memory and the nervous elements of the sensitive and motor phenomena of the organism. Reflection on the physical mechanism underlying mental operations of various kinds, demands the vitalistic explanation much more than the physiological phenomena which have converted physiologists to the old way of thinking in our time. Our individuality is probably largely due to the physical basis of our mentality, but there is something more than that required for any theory of mental operations that would satisfy all the questions that come to us. There is, then, actual proof of the existence of a force that is part of us, that constitutes a bit of the essence of our personalities, yet is capable of accomplishing results that we cannot understand, and of managing a machine that transcends any physical powers that we can think of. [Illustration: FIG. 22--MOTOR CELL OF VENTRAL HORN OF SPINAL CORD FROM THE HUMAN FETUS, THIRTY CENTIMETERS LONG (method of Golgi; after von Lenhossek. Barker.)]