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80 physiological tetanus find in the phenomenon of the so-called muscle sound. This was first observed by the celebrated Dr. Wollaston, a prominent man of science of his day, and one of those who took a deep interest in this Institution in its earlier years. His bust is on the staircase. He discovered that when a muscle contracts, and is maintained in a state of tension, it gives out a sound or tone. We can hear it by placing the ear over a muscle, like the biceps of a muscular person; or, in the dead of night, when all is still, by strongly pressing the teeth against each other by clenching the muscles of the jaws. You may hear it, I believe, simply by putting the tips of the index fingers into the ears and then contracting the muscles of the arms. Now you are aware that the pitch of a tone is determined by the number of vibrations per second made by the body that vibrates and gives out the tone. This tuning-fork, for example, vibrates 128 times per second and gives out a tone of low pitch, while this other one vibrates 8 times as fast, or 1004 vibrations per second, and consequently gives a tone of much higher pitch. The pitch of the muscular tone indicates that