The first change to be observed is in the vascular system and within the vessels themselves; this begins with a widening of the small arteries, then of the smaller capillaries and veins. This increases the current of blood with greater velocity through the widened vessels. Sooner or later this rapidity of the current lessens; there is a marked slowness to be observed in the stream. The single or separate blood cells, which in the beginning of the observation could not be distinguished, can now be distinctly seen, especially in the veins and small capillaries, in which, from the slowness of the current, the blood accumulates. In the veins there now appears at the periphery of the current a pellucid plasmatic layer, in which there are white blood cells, that have separated themselves from the main current; the white cells either float slowly along or adhere to the walls of the vessels. This phenomenon the Germans term “Randstellung der Farblosen Blut Körperchen,” which means, bordering of white blood corpuscles. Not long after the “bordering” of white cells, a change takes place in the cells themselves, that is very interesting. The white cells become elongated and spear-shaped at one extremity, which pierces the wall of the vessel, and after a little while the sharp extremities will appear on the outer surface of the wall of the vessel, and a little later on, indeed, the entire protoplasmic cell will have emigrated into the tissue, outside of the vessel. Or, in other words, the colorless blood cells will have passed through the walls of the vein or capillary, and this constitutes an _extravasation_. The first extravasated cells will soon be followed by others in great quantity, so that in six to eight hours veins and capillaries are surrounded with white corpuscles. In their normal destination these become organized into fibrous or granulation tissue; and for this reason, an organ that is the seat of chronic inflammation becomes immensely enlarged from this inflammatory accretion. We can now readily appreciate why the womb, liver or kidneys become augmented in size from inflammatory processes. Indeed, this applies to all growths and even to bone, and if a part is injured by a cut, accident or disease of some sort, precisely the same processes are at work to repair the lost tissue. It cannot fail to become apparent at once, that to understand the phenomena of inflammation is to possess the key that opens to our understanding the operations not only of most diseases, but of the healing processes of wounds and injuries. In the course of the experiment we see also red blood corpuscles transude, which are always accompanied with more or less fluid or plasma.