I have noticed a curious tremor during inspiration in suffering men and animals. I have found it in a less degree also in healthy animals, particularly in dogs. At every inspiration there is a very noticeable tremor of the limbs and of nearly the whole muscular system. The excitement arising in the nerve-centres to produce a contraction of the diaphragm and of the muscles of the thorax seems to have become so strong, that it goes beyond the limits of the respiratory centre and diffuses itself over a great part of the nerves. In anger, fear, and mental perturbations, when the stormy winds of passion rage, waves flow to all parts of the nervous system, then break, revealing themselves in the agitation of the muscles. Trembling often has a peripheral origin, and may be due to both heat and cold. It is sufficient to hold the arm in water heated up to 48° or 50° in order to produce a visible tremor. This fact, which I observed repeatedly on my brother, corresponds to the chattering of the teeth when a cold stream of air strikes our face. V Very excitable dogs often tremble when another dog approaches. I know one that trembles like a leaf whenever, from the height of a second floor, he sees a bigger dog passing in the street. This lively alarm is quite pitiable, and after all most unnecessary, for the most of his supposed rivals do not perceive his presence, nor even look up. But as soon as he catches sight of them in the distance, he becomes suspicious, a feverish shiver goes over him, the hair on his back stands on end, his whole body trembles, while he cowers near the window with ears erect, looking fiercely out of the corners of his eyes, snarling, and showing his teeth--a ridiculous instance of timid arrogance and despised pride.