In many cases, the other systems being irritated, the animal sensibility of this is brought into action. Among the numerous examples of this fact, the following is a remarkable one. In many diseases in which organs foreign to the mucous system are affected, we experience a sensation of burning heat in the mouth, the stomach, the intestines, &c. and yet the mucous surface, the seat of this sensation, does not disengage more caloric than usual; we may be convinced of this by placing the fingers in the mouth. This sensation is of the same nature as that which we refer to the glans penis when there is a stone in the bladder, as that which is experienced at the end of the nose from worms in the intestines, &c. There is no material cause of pain, and yet there is suffering. Thus in intermittent fevers we experience a cutaneous shivering, though the skin may be as warm as usual; I would observe in respect to this, that the mucous membranes are hardly ever the seat of an analogous sensation of sympathetic cold, but it is almost always a sensation of heat that the aberrations of the vital forces produce in them. Whence arises this difference between them and the cutaneous organs? I know not. I attribute also to a sympathy of animal sensibility the great thirst which takes place in all the severe affections of any part. In all great wounds, after severe operations, in experiments on living animals, &c. we observe this thirst which depends upon a sympathetic affection of the whole mucous surface that extends into the mouth, the stomach and the œsophagus. Animal contractility cannot be put sympathetically into action in the mucous system, since it does not exist in it. The same is true of the sensible organic contractility. It is possible that sometimes the kind of motion we have noticed, and which resembles this property, may be sympathetically excited; I know no example of it.