It is to the susceptibility of the brain and nerves of still transmitting the principle of motion after death, that must be referred all the phenomena that are witnessed in the different kinds of decapitation. Ducks, geese and other animals of this family move their muscles with some regularity, after the head is taken off, in running, jumping, &c. Some time after the punishment of the guillotine, the inferior and superior extremities are still the seat of various tremors; the muscles of the face are sometimes even contracted so as to give to this part the expression of certain passions, an expression incorrectly referred to the sensitive principle still left for some time in the brain. The same phenomena were formerly observed in the punishment that consisted in cutting off the head with an axe. During the year past I have had a painful proof of these singular facts; a guinea-pig, whose heart I had just removed, plunged deep into my finger the four prominent teeth that distinguish this species. All these phenomena are only the result of the irritation produced, either by the cutting instrument, or by the air, upon the two divided extremities of the marrow; this is so true, that by increasing the irritation by a pricking, cutting instrument, &c. with a chemical agent applied to these extremities, the motions are very much increased. Nothing is more easy than to be convinced of this fact in an animal; I have many times proved it in those who have been guillotined, upon whom I have been allowed to make experiments for galvanic purposes. See how the alternate motions of respiration can continue for some time, after the brain has been destroyed, after a wound of the head in which its mass has been crushed, after a luxation of the first vertebra, in which the beginning of the spinal marrow has been compressed so as suddenly to stop life, after the injection of a very irritating fluid by the carotid, &c. &c. In this duration of animal contractility after death, the muscles are absolutely passive; they obey, as during life, the impulse they receive from the nerves; it is this which distinguishes it essentially from the duration of irritability, a property by which, after death as during life, the muscle has in it the principle which makes it move. The duration is greater or less according to the class of the animals; those with red and cold blood keep this property longer than those with red and warm blood; among these, the family of ducks are, as I have said, remarkable for this phenomenon, which is much more rapidly lost in the others and in quadrupeds. In the first class there are also varieties among the reptiles, fishes, &c.