The manner in which caloric enters the body, is of no consequence. Vegetables that have no lungs, but only air tubes and absorbents, and fishes that have branchiæ, have an independent temperature. That heat may be produced, it is sufficient that foreign substances are continually assimilated to the fluids of organized bodies, and that after this assimilation, these fluids, whether they are blood, as in animals with red blood, either warm or cold, or whether they are of a different nature, as in those with white fluids and in plants, it is sufficient, I say, that the fluids undergo different transformations in the capillary system. Respiration combines more caloric with the blood; there is consequently a greater disengagement of this principle in animals who breathe by lungs, than in others; and even in the first, the greater the lungs, the greater is the quantity of caloric disengaged; as is proved by comparing birds, quadrupeds, the cetaceous tribe among fishes, &c. But these varieties are certainly only in relation to the degree of temperature; hence there are animals with cold blood, and those with warm. The general phenomena of the disengagement of heat remain always the same in animals with lungs, in those without them, and in plants. From these principles, it is easy to understand most of the phenomena of animal heat. The disengagement of caloric is always subordinate to the state of the vital forces. As the tone of a part is greater or less, it is more or less warm. This dependance of the heat upon the state of the forces of the part, is a fact, that is proved by all diseases and all the phenomena of health; it is as true with regard to heat, as it is with regard to the exhalations and the secretions. The greater afflux of blood to an inflamed part and the greater disengagement of caloric, the increase of this disengagement in the womb and the nose, and menstruation and the active nasal hemorrhages, &c. the heat of the chest and active pulmonary hemorrhages, &c. are the effects of the same cause, viz. the increase of the vital forces of the part. In general, whenever the tone is much increased, the heat increases also; hence why there is a greater disengagement of it in almost all active sweats, hemorrhages, and even secretions; whilst this fluid is not superabundant in sweats, hemorrhages, or secretions that are called passive, whatever may be the quantity of fluid separated from the blood by them. Each system has its own degree of heat. There is certainly less caloric given off in the hair, the nails, and the epidermis, than in the other systems. The white organs, as the tendons, the aponeuroses, the ligaments, the cartilages, &c. have probably less than the muscles. Examine the claws of birds, in which there are only these white parts; they are not so warm as the rest of the body.