This then is the cause of a fever in the general sense; and thence we shall be led to understand what this disturbance in its nature actually is; namely, an unnatural action of the solids upon the fluids. Now as the fluids are the most yielding parts, that must submit to the pressing motion of the solids, we may without much difficulty, see one principle reason of its being set into a disturbed commotion, when the irritability of the nervous fibrillæ are acted upon. Again, when we consider that the blood is liable to become acrimonious, and thence by its stimulus apt to act upon the coats of its containing vessels, we see demonstratively plain, how the solids are subject to be excited to act upon the very blood that stimulates them. Moreover, as motion must naturally produce heat, and heat motion, and motion expansion, and expansion rarefaction, we at once bring to view the principal laws of mechanism, that governs the human automaton in the various degrees of health as well as disease. However, let me not forget to whom I write, but haste to the point I am at. A fever may proceed from many different causes, and may affect many different constitutions, and also produce many different effects; it is therefore just that a proper distinction should be made. Indeed, it is a subject that cannot be too minutely handled; because it is scarce possible that there is a disease void of a fever in some degree or other.—But preciseness and utility is the object I have in view. ------------------------------------------- SECT. II. _Of Accidental Fevers._ How uncertain is human life! One moment in a perfect state of health, the next perhaps no more; or confined under the painful sensations both of body and mind! Every accident is liable, and unavoidably must bring on a fever; and this, like fire, should be extinguished in its earliest commencement. But in that, as I have before observed, the constitution should principally be consulted. I have in the lecture of accidents, at every opportunity, recommended bleeding, but always with a proviso, _if requisite_; and, as this is of more consequence than generally is supposed, I find it necessary here to expatiate farther on it.