It is not true that laughing and weeping are exclusively human. One need only observe attentively the face of a sensitive and faithful dog in order to see the first traces of expressions betraying an altered state of the nervous system. In joyful emotion, as, for instance, when he meets his master, the lips are lifted in such a manner as to uncover the teeth, the head inclines in a caressing attitude, the rhythm of the respiration is modified, and the eyes glisten. Notwithstanding the difference of anatomical structure and the wide dissimilarity of parts, we can yet trace in the dog the rudiments of those involuntary muscular movements which attain their supreme expression in man, in whom a slight movement of the muscles curves the lips into a smile which sheds a ray of benevolence over the whole face and increases the charm of beauty, as though with the breath of love itself. Darwin wrote many interesting pages about the way in which monkeys laugh. Humboldt observed the eyes of a monkey fill with tears when it was overcome by fear, and Brehm relates that seals weep with pain, and that young elephants when ill-treated shed tears as abundantly as man. V Their reasons why changes in the psychical state are reflected are numerous with such facility by the muscles of the face. Besides that of proximity to the nerve-centres propounded by Spencer and Darwin, there is the anatomical fact that the facial muscles have, for the most part, no antagonists. We know that in the hand, for instance, a slight contraction of the muscles which serve to open the hand and extend the fingers, is opposed by the action of the flexors which bend and contract the fingers. In the face the majority of the muscles can act freely, hence a slight nervous shock produces effects far more intense than in the other muscles of the body, in which the slight contraction of muscles acting in a contrary sense must always be overcome. The muscles of the face are also more delicate, and have less volume than those of other parts of the body. Now the volume of the muscles exercises considerable influence on the greater or lesser facility with which they contract. A convincing proof is offered by the heart, in which, when life ceases, there is an almost immediate stoppage of the action of the ventricles, which form a thick, firm muscle, while the auricles, forming a fine muscle, continue to move for hours after all other parts are rigid in death.