Let it not be thought, from these allusions, that I admit Dr. Cullen's supposed vires naturæ medicatrices to have the least agency in this re-action of the blood-vessels. I believe it to be altogether the effect of their elastic and muscular texture, and that it is as simply mechanical as motion from impressions upon other kinds of matter. That the blood-vessels possess muscular fibres, and that their irritability or disposition to motion depends upon them, has been demonstrated by Dr. Vasschuer and Mr. John Hunter, by many experiments. It has since been proved by Spallanzani, in an attempt to refute it. Even Dr. Haller, who denies the muscularity and irritability of the blood-vessels, implies an assent to them in the following words: "There are nerves which descend for a long way together through the surface of the artery, and at last vanish in the cellular substance of the vessel, of which we have a specimen in the external and internal carotids, and in the arch of the aorta; and from these do not the arteries seem to derive a muscular and convulsive force very different from that of their simple elasticity? Does not it show itself plainly in _fevers_, faintings, palsies, consumptions, and passions of the mind[2]?" [2] First Lines, sect. 32 of the chapter on arteries. The re-action or morbid excitement of the arteries discovers itself in preternatural force, or frequency in their pulsations. In _ordinary_ fever, it is _equally_ diffused throughout the whole sanguiferous system, for the heart and arteries are so intimately connected, that, like the bells of the Jewish high-priest, when one of them is touched, they all vibrate in unison with each other. To this remark there are some exceptions. 1. The arteries are sometimes affected with great morbid excitement, while the natural functions of the heart are unimpaired. This occurs in those states of fever in which patients are able to sit up, and even to walk about, as in pulmonary consumption, and in hectic fever from all its causes. 2. The heart and pulmonary artery are sometimes affected with great morbid excitement, while the pulsations of the arteries on the wrists are perfectly natural. 3. The morbid excitement of the arteries is sometimes greater on one side of the body than on the other. This is obvious in the difference in the number and force of the pulsations in the different arms, and in the different and opposite appearances of the blood drawn from their veins, under equal circumstances. 4. The arteries in the head, lungs, and abdominal viscera are sometimes excited in a high degree, while the arteries in the extremities exhibit marks of a feeble morbid action. Fevers attended with these and other deviations from their common phenomena, have been called by Dr. Alibert, _altaxiques_. They occur most frequently in malignant fevers.