The nervous system with all its wonderful and elaborate mechanism has one function or purpose; viz.: to enable the organism to act. Whether we consider the most primitive nerve structure in the lowest animal in which nerve substance has been found, or the most elaborate brain of the most intellectual man, it is the same. To facilitate action is the end and aim of all nerve structure —of all the processes that go to make up what we call mind. The sensations, the perceptions, the ideas, the at­ tention, the memory, the judgment, the reason, the imag­ ination, all are processes that exist not for their own sake but purely and solely for action. The actions which stimuli produce vary in complexity according to (1) the complexity and (2) the use made of the nervous system. In other words, the perfection of action depends upon the elaborateness of the neuron pattern which in turn is the result of (1) inheritance and (2) the experience of the individual.