Page:Popular Science Monthly Volume 42.djvu/777

Rh of muscles, and, as Prof. Goodsir used to point out, the muscles of the back, so perplexing at first, are really quite simple in their arrangement. For each of the spinal vertebræ has to be bent and straightened and has also to rotate more or less upon its neighbors, so as to allow the upper part of the body to swing round upon the lower. We have, therefore, muscles going from the spine of one vertebra to the spine of the next, and then muscular strips stretching over a few and then over many vertebræ, so as to straighten the spine either in part or whole, as the movements may require. A similar arrangement holds good for the muscles passing from the spines to the lateral processes and which rotate the vertebræ on one another.

But if we are to group the muscles and nerves of the body into one easily remembered whole, we must see what is the chief function to be subserved by them, what is the center of the little universe which they compose. The function of most imperious necessity is respiration. A man may starve himself to death, but he can not kill himself by holding his breath. He may refuse food, but can not refuse air. In the child the function of respiration is the first which evidences itself after birth, and the muscles which subserve it are more fully developed and more perfectly innervated than others. The nerve channels which supply them are, as it might be termed, more deeply grooved than others, and it is along these channels that superabundant energy overflows in the movements of laughter which evidence joy. This has been very fully and wisely explained by Herbert Spencer in his essay on Laughter. But the great poet, whose recent death the whole civilized world is now deploring, has classed together in a few pregnant words the channels through which the overflow of energy may run in their proper order. In describing the joy evinced by a baby on seeing its mother, Tennyson says it

The very parts which attain to the highest development in adult age, and are capable of the finest and most dexterous movements, are the last to develop, and in infancy they are well described as "lazy lingering fingers." They take no part in the function of