An ulcer having been defined as a surface which is or ought to be granulating, it becomes necessary to define the granulation process and to show how healing is thereby achieved. _Granulation tissue_ is a name applied to a new and temporary tissue of embryonic type, which acts as a scaffolding or temporary structure, permitting the construction of more permanent tissue. It is produced entirely by the activity of cells, which are the mononuclear and polynuclear leukocytes and the wandering cells already mentioned. They are frequently known as _embryonal cells_ when performing this function; sometimes as _formative cells_. They have a distinct nucleus, which stains readily, and, having this resemblance to epithelial cells, they are often referred to as _epithelioid cells_--sometimes as _fibroblasts_, because they may later assume the dignity of connective-tissue cells. They assume a multitude of shapes. Between these cells as they are drawn toward the point at which they are most needed, perhaps by chemotactic activity, there is an _intercellular substance_ which later becomes fibrillated. As these fibers develop the remaining cells become entangled between them, and in this way a new connective tissue is formed of cells of originally mesoblastic origin. Of such tissue the solid part of granulation tissue is built. This tissue is essentially different from the epithelium which it is expected will subsequently cover it. If a normal granulating surface is scanned with a magnifying glass of small magnifying power, it will be seen to consist of numerous minute projections, each of which is known as a granulation, consisting of the tissue above described, formed as a minute eminence around a budding capillary bloodvessel, from which a projection has arisen upon the exposed surface. This capillary bud is the result of karyokinetic activity on the part of the endothelium--namely, the hypoblastic cells of which it is essentially composed. In each of these cells, under certain circumstances, the karyokinetic threads already mentioned develop and become loosely coiled, while the chromatin in the nucleus increases in amount and the nucleolus disappears. The chromatin threads become thicker, arrange themselves equatorially around the poles of the nucleus, and gradually turn so as to point toward it, while a new membrane forms around each separate coil, and two nuclei are thus made out of one. While this is taking place within the nucleus the cell protoplasm undergoes active rotary motion, is finally segmented, and by the time the nucleus is divided is nearly ready for complete division of the cell. While nuclear division is usually bipolar, it may be multipolar; if a rearrangement of the protoplasm is delayed, the result becomes a multinuclear cell, known as a _giant cell_.