2. By the habits of the persons who are most subject to such fevers. 3. By the theory of fever. I have attempted to prove that the higher grades of fever depend upon morbid and excessive action in the blood-vessels. It is connected, of course, with preternatural sensibility in their muscular fibres. The blood is the most powerful irritant which acts upon them. By abstracting a part of it, we lessen the principal cause of the fever. The effect of blood-letting is as immediate and natural in removing fever, as the abstraction of a particle of sand is, to cure an inflammation of the eye, when it arises from that cause. 4. By the symptoms of the first stage of violent fevers, such as a sleepiness and an oppressed pulse, or by delirium, with a throbbing pulse, and great pains in every part of the body. 5. By the rupture of the blood-vessels, which takes place from the quantity or impetus of the blood in fevers of great morbid action. Let no one call bleeding a cruel or unnatural remedy. It is one of the specifics of nature; but in the use of it she seldom affords much relief. She frequently pours the stimulating and oppressing mass of blood into the lungs and brain; and when she finds an outlet for it through the nose, it is discharged either in such a deficient or excessive quantity, as to be useless or hurtful. By artificial blood-letting, we can choose the _time_ and _place_ of drawing blood, and we may regulate its quantity by the degrees of action in the blood-vessels. The disposition of nature to cure violent morbid action by depletion, is further manifested by her substituting, in the room of blood-letting, large, but less safe and less beneficial, evacuations from the stomach and bowels. 6. By the relief which is obtained in fevers of violent action by remedies of less efficacy (to be mentioned hereafter), which act indirectly in reducing the force of the sanguiferous system. 7. By the immense advantages which have attended the use of blood-letting in violent fevers, when used at a proper time, and in a quantity suited to the force of the disease. I shall briefly enumerate these advantages. 1. It frequently strangles a fever, when used in its forming state, and thereby saves much pain, time, and expence to a patient. 2. It imparts strength to the body, by removing the depression which is induced by the remote cause of the fever. It moreover obviates a disposition to faint, which arises from this state of the system. 3. It reduces the uncommon frequency of the pulse. The loss of ten ounces of blood reduced Miss Sally Eyre's pulse from 176 strokes to 140, in a few minutes, in the fever of the year 1794. Dr. Gordon mentions many similar instances of its reducing the frequency of the pulse, in the puerperile fever. 4. It renders the pulse more frequent when it is preternaturally slow.