THE STORY OF THE BRAIN AND NERVE 121 



over to the carting and packing departments of the 

 business, the men engaged representing the lowest 

 grade of employe's. We may suppose that the second 

 storey is given over to the routine business of the 

 firm discharged by clerks and heads of departments. 

 Above this, in turn, would come the offices of the 

 heads of the firm and the partners. Applying this 

 simile to the brain itself, we find that the chief lower 

 centres situated at the base of the brain and upper 

 part of the spinal cord are known as the medulla 

 oblongata (Fig. 32). If we include the cerebellum 

 (Fig. 33) along with the medulla we may arrive at 

 some conception of the resemblance of those parts 

 to the lower storey of the warehouse. The medulla 

 is a highly important centre whence arise important 

 nerves, among them the vagus nerve controlling 

 the heart's action, breathing, and other actions. 

 We can therefore understand why an animal 

 that is born with the medulla developed, but the 

 rest of the brain absent, may live for some days 

 because its breathing, the heart's action, and 

 swallowing may be controlled. The cerebellum is 

 the part of the brain exercising what is called the 

 co-ordination of movements, by which term is meant 

 the bringing into harmonious action of different 

 muscular movements of the body. The power of 

 bringing the muscles of one side of the body into 

 regulated action with the muscles of the opposite 

 side, as in walking, in swimming, and in flying, is due 

 to the control exercised upon them by the cerebellum. 

 It is to be noted that the cerebellum does not confer 

 the power of bringing these muscles into action. 

 That duty is accomplished by centres in the cere- 

 brum specially devoted to their regulation. The 

 cerebellum in this respect is like the driver of a coach 



