RELATIONS AND STRUCTURE.--These tumors grow from the muscular and connective tissues of the uterus, and consequently partake of the character of these tissues. Sometimes the substance of the tumor consists principally of connective, at others of muscular, tissue. The variations in the relative proportion of these two fibrous substances constitute the main differences in the characters and appearances of the tumors, and lead to the different terms applied to them, as myomata, fibromata, myo-fibromata, etc. The firmer the tumor the more connective tissue it contains. When we inspect, either ante- or post-mortem, a uterus with a fibrous tumor attached or contained within its wall, it will be found to present a much darker hue than natural. Instead of the normal light rose-color, it is generally dark, sometimes almost of a purplish tint. The time of menstruation makes some difference; just before it is darker than soon after the menstrual flow. The color also varies with the character and size of the tumor. In large solid tumors the color is darker than in the large fibro-cystic variety; indeed, in some of the latter the pearly color strongly reminds one of an ovarian cyst. We cannot therefore depend on the color or shape of surface for a diagnosis. Even after the abdominal cavity is opened the contour of the uterus is usually not regular. If we make an incision into the tumor, we find that it is surrounded by a distinct capsule, which limits and defines its boundaries and separates it from the adjacent substance. This envelope is not a cyst or other form of membrane: it is continuous with, and inseparable from, the muscular structure of the uterine walls. It, in fact, is a condensed layer of the fibrous substance of the uterus. In cases of true encysted tumors the cyst-wall is the generating portion of the growth. In fibrous tumors of the uterus the growth produces the capsule by displacing the surrounding substance in every direction, pressing it strongly against the unaffected fibrous tissue and condensing it into the smooth capsule. It is thus engendered in, and enveloped by, the muscular walls of the uterus. These latter of course grow to dimensions sufficient to keep pace with the increasing tumor. The growth may, as a consequence of such a connection, be hulled out or enucleated, and will not be reproduced. Inflammation or other degenerating processes may occasionally cause adhesion of the capsule and tumor, but this is an accident of uncommon occurrence. To understand this mode of encapsulation we must remember that the uterine muscles are irregularly stratified, {246} and that the tumors are developed between the strata as between the leaves of a book, separating them sufficiently to gain lodgment and room.