Now, with respect to this theory, which has deservedly had vast influence in regulating the judgment of professional men on the nature of the process called inflammation, it cannot be received in the present state of knowledge without some limitation. The hypothesis that the bloodvessels possess an active power of dilatation, independently of their elasticity, must as yet be regarded as devoid of proof, and, therefore, should not be assumed as a basis on which any theory of inflammation can be founded; and as a writer has truthfully remarked, "How different would have been Dr. Hunter's inferences if, instead of trusting to the unassisted eye, he had viewed the inflamed vessels through a microscope." He would then have seen the blood moving, and, instead of its passage being quickened in the inflamed parts or vessels, he would have found it uniformly rendered slower in proportion to the degree of inflammation, and in the most inflamed parts stasis, or complete stagnation, being the result.

In modern times, the vague but convenient expression "increased action of the vessels," has been very generally used as an adequate expression of the proximate cause of inflammation. The doctrine, it is said, derives support from a review of the several exciting causes of inflammation, which, being in general of an irritating nature, must, when applied to any living or sensible parts, occasion such increased action of the vessels, while the method of cure also tends to confirm the opinion. Hut berfore one can judge whether this doctrine is correct, and supported by facts and observations, it is necessary to understand precisely what is implied by in-creased nation of vessels; for it is not every affection of the vessels, capable of being thus denominated, which will of itself constirute inflammation. For example, during gestation the artories of the womb are enlarged, and a greater quantity of blood is sent into them, yet this organ is not inflamed. Other examples may be cited, but for all practical purposes the one already given is sufficient. If, then, the proximate causes of inflammation is to be called an increased Motion of the vessels, wo must first be informed not only what is mount by the term, but what particular vessels are spoken of, whother the arterial trunks, branches, or capil-larles: beeuuen, if the phrase is intended to signify increased alternate expansions and contractions of all the arteries of the Inflamed part it is a hypothesis entirely destitute of foundation; or if it ho mount to denote an increased velocity of the motion of the blood in the part affected, the doctrine in ruther contradicted than continued by the latest and most carefully instituted microscopical experiments. But if the expression refers only to tho dilated state of the capillaries, the throbbing of the arteries leading to the seat of inflammation, the otttision of lymph, etc., loss fault can be found with the language, though yet requiring much further explanation ere it can communicate any precise information.

"There are," says a learned professor, "two suppositions which at present divide the opinion of pathologists respecting the state of the capillary vessels affected with inflammation, According to the first of these suppositions, the inflamed vessels are in a state of increased action. According to the second. they act with less force than the trunks from which they are derived." The first of these opinions, according to Dr. Thomson, was suggested by the views which Stahl took of the animal economy, and his ideas respecting the tonic or vital action of the capillary vessels. The doctrine, however, was more particularly insisted upon by his disciples and followers, especially Dr. Garter, who, in one place, expressly states, "that the proximate cause of inflammation consists in an increased vital action of some particular artery or arteries, by which the blood is propelled with greater force than usual into the communicating lymphatic and colourless vessels." Again Dr. Thomson says: "There are certain points in which the two doctrines agree, as well as others in which they differ."

The advocates for each hypothesis agree in admitting; First, that inflammation has its seat in the capillary vessels; and second, that the redness in inflammation is owing to an unusual quantity of blood in the vessels of the inflamed part, and consequently that the capillary arteries are much dilated during the state of inflammation. The contractions of these vessels, indeed, it has been said, are increased also in a ratio proportional to the dilations, but this is an assertion which has not yet been proved, either in the way of experiment or of observation.

The sense of throbbing which the advocates for the hypothesis of increased capillary action regard as the strongest proof of that action, are disposed to attribute it to the difficulty which the blood meets with in passing from the trunk to the capillary branches. This sensation of throbbing and appearance of increased action may be produced in an instant by tying a cord round an uninflamed finger, so as to obstruct the motion of the blood through it; besides, this throbbing, or pulsatory motion, can afford us no criterion by which to judge of the force with which the arteries contract, for it is produced by the dilations also, and by a power foreign to the artery itself.

Dr. Philip gives the following definition, namely: "Inflammation seems to consist in the debility of the capillaries, followed by an increased action of the larger arteries, and is terminated by resolution when the capillaries are so far excited, and the larger arteries so far weakened by the preternatural action of the latter, that the power of the capillaries is again in due proportion to the vis à tergo." "Thus far," says the same writer, "I cannot help thinking the nature of inflammation appears sufficiently evident. The motion of the blood is retarded in the capillaries in consequence of the debility induced in them; an unusual obstacle is thus opposed to its motion in the arteries preceding them in the course of the circulation, which are thus excited to increased action."