Page:Popular Science Monthly Volume 42.djvu/779

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STRUCTURE, ACTION, AND THOUGHT.

more easy to discuss the actors in the scene by the names of Adam and Eve, than by the terms "male" and "female frugivorous animal."

Let us take then the story from Genesis. One day Eve went into the garden of Eden—saw an apple upon a tree—plucked it, ate it, and then went to get another for Adam. In trying to analyze the muscles concerned in these acts, the easiest way is to go to your bedroom, strip off your clothes, imitate Eve's action, and as you do so, feel out the individual muscles as they contract under the skin. This plan of learning the muscles is one which I used to follow as a student of anatomy, and I found it a very useful one indeed. If you do this you will find the muscles of the neck, shoulder, arm, forearm, and hand contracting successively or together in co-ordinated movements, which are beautifully adapted to the purposes just mentioned. We might take the muscles which produce these movements one by one, but I think it is easier for the purpose of grouping them, though not so good for the purpose of study in your own room, to consider first of all the motor centers in the brain from which the stimuli proceed. Before proceeding to consider these I wish to draw your attention to the errors into which one may fall regarding the action of muscles as well as of the motions of the planets by regarding them from a wrong point of view. Thus, the action of the tensor vaginæ femoris is usually said to be that of rotating the thigh inward upon the bodyPSM V42 D779 View of a Lobe of the Cerebrum.jpgFig. 10.—View of a Lobe of the Cerebrum from the Longitudinal Fissure. (After Horsley and Schäfer.) and thus turning the foot and toes inward also, an action which is denounced in all calisthenic exercises. But this muscle was not introduced into the body for the sole purpose of plaguing drill sergeants and dancing masters. As the late Prof. Sharpey used to point out, we ought to look its action from the leg as a fixed point, and then we discover its true uses at once. Place your hand at the side of the hip over the muscle and march forward. You will then find that when one foot is planted firmly on the ground the corresponding muscle becomes tense whenever you lift the other leg and try to advance it. Whenever the other foot is raised the