Looking to the cardinal signs of inflammation already enumerated, it will appear that two of them, namely redness and heat, are intimately related to the condition of the circulation, while the swelling may possibly have similar relations. John Hunter, in his conceptions of inflammation, regarded the phenomena as essentially connected with the state of the blood and blood-vessels. On the other hand, Virchow in his great work on cellular pathology emphasized the importance of the tissues, and regarded the phenomena of inflammation as due to a stimulation of the cells. Under the influence of the discovery, by Cohnheim, of the emigration of leucocytes from the vessels there was a revulsion towards the vessels, and the attempt was made by this author to limit the term inflammation essentially to the phenomena connected with the vessels, and to regard it as a disturbance of the circulation. Still more recently Metchnikoff has attempted to limit inflammation to the activity of the amoeboid cells of the body in their attempts to deal with intruding agents. He thus reduces inflammation to a process of Phagocytosis. In forming a complete picture of inflammation it is necessary to consider the whole phenomena in which vessels, tissues, and phagocytes will all have their parts.

A simple Experiment may be performed to illustrate the principal phenomena at the outset of an acute inflammation. If a frog be paralyzed with curare, the web of the foot may be spread out and observed under the microscope. With a pair of scissors a superficial longitudinal wound may be made, taking care to remove little more than the epithelium. By this operation the connective tissue of the web, with its vessels, is exposed; the action of the scissors in cutting and the unusual exposure to the air, affect these structures, and the various phenomena of inflammation soon begin to manifest themselves, care being taken to keep a moist atmosphere around the web so as to prevent the wound, deprived of its epidermis, from drying. At first the circulation goes on in the bottom of the wound as before, the area is merely more transparent from the absence of the epithelium. But very soon, if an artery is near or in the wound, it dilates, and there is an acceleration of the stream in the capillaries and veins. But this soon disappears, and the circulation, especially in the capillaries, becomes slower and slower, till here and there the blood-corpuscles now and then stand still for a moment or two. By and by a peculiar condition becomes visible in the veins. Normally, the blood corpuscles flow down the middle of the vein, and the peripheral zone contains plasma with a few white corpuscles rolling along. As the inflammation proceeds, the white corpuscles come to occupy this zone, and to adhere to the inner surface of the vessel. The individual corpuscles may not be all absolutely stagnant, they adhere for a time and then depart, but the result of the process is that there is a nearly complete filling up of the zone with white blood-corpuscles, so that the vein seems pave-mented internally with these cells. This is seen not only in any vein which may happen to be in the bottom of the wound, but also in those for a short distance outside it.

If the attention be now directed to the surface of the wound it soon becomes manifest that certain peculiar bodies are appearing there.

These are at first seen mostly towards the edge of the wound, and are especially numerous in the neighbourhood of veins where the white corpuscles are adherent. They are of various shapes, and present a transparent gelatinous appearance. If observed carefully they are seen to be altering their shapes, presenting the well-known amoeboid movement, as shown in Fig. 56. These cells gradually increase in numbers, and by their contractile power, they move from the periphery towards the centre of the wound till they may come to cover it entirely. These bodies may be removed from the wound by placing the end of a capillary glass tube on the surface. A fluid runs up into the tube, and in this fluid are these free cells. The fluid may now be blown on to a glass slide and examined under a higher power of the microscope, when the slow amoeboid movement will be still more manifest. If, in the drop of fluid, the bodies are allowed to die or are killed by the addition of a reagent, they become globular and granular, in fact, have the characters we recognize as those of white blood-corpuscles, lymph corpuscles, pus corpuscles - of leucocytes in general. The addition of acetic acid to the living cells will first cause them to assume the globular form, and then will bring out the nucleus or nuclei as in an ordinary white corpuscle. The fluid in which these corpuscles are found is coagulable, and if it be kept till the corpuscles have died strings of fibrine will be found in it. If this experiment be made in summer, the whole of those phenomena will manifest themselves in a few hours, and' in five or six hours the entire wound may be plastered over with amoeboid cells. In the course of a few more hours the wound begins to be covered in with new-formed flat epithelium. This begins at the margins, and if the wound is small it may be wholly covered within twenty-four hours. The amoeboid cells are covered in, but they very soon disappear, and the connective tissue of the web remains with a thin transparent epithelium covering it.

Without following out this experiment further, we may now proceed to consider the principal phenomena of inflammation, which have been partly illustrated. We shall consider, first, the state of the vessels; secondly, the condition which is illustrated in this experiment by the fluid on the surface of the wound containing amoeboid cells; and lastly, the condition of the tissues in inflamed parts.