3rd var. Sub-mucous fibroid.—In this va riety the fibroid mass quits its bed in the uterine walls, and projects into the cavity of the uterus ; it becomes covered by an exten sion of the lining membrane of' the uterus, and sometimes also beneath this by a layer of healthy uterine tissue. These tumours, when they possess a peduncle, constitute the fibroid polypi of the uterus.
A distinction has been made in these po lypi between such as form continuous out growths from the substance of the uterus, and those in which the polypons mass forms a discontinuous tumour, connected only by a narrow stem of mucous and muscular tissue.
The original position of the fibroid growth in the uterine walls, whether in the middle or nearer to their inner or outer surfaces, proba bly determines, in a great measure, the direc tion and form which these growths ultimately take, and is consequently productive of the three varieties above noted.
The different forms which fibroid assumes are in accordance with these varieties of po sition. Fibroid growths retained within the uterine walls, are at first almost invariably spherical, but in course of growth become ovate or flattened. Those which project from the outer surface are usually nearly round, hile the polypi of the cavity, and those which extend into the vagina, are pyriform, and possess longer or shorter peduncles. The greater part proceed from the fundus, com paratively few from the walls of the body, and scarcely any of this kind from the cervix. The latter are usually of a more spongy, or cellular character than the former, which con sist of a denser fibrous tissue.
The power of growth of fibroid tumours appears to be nearly unlimited. The known extremes in such cases are, in point of num ber, from one to forty ; and in respect of weight, from a few grains to seventy pounds.
Fibroid exercises a considerable influence upon the form and position of the uterus. Tumours within, or external to it, change the position of the organ in various ways, pro ducing elevation, prolapsus, lateral obliquity, and especially retroversion, according to the seat which they occupy. Polypi distend the cavity of the body and cervix, and the os uteri, and sometimes produce prolapsus and inversion of the uterus.
The influence of fibroid upon the thickness of the uterine walls is also considerable. Ge
nerally a marked hypertrophy, equal some times to that of pregnancy, takes place, while in parts a thinning of the walls occurs. The latter is especially observable in cases where the tumours are numerous, as in fig. 476. These sometimes appear to grow at the ex pense of the whole uterine substance, so that the original organ is with difficulty discovered among the hypertrophied mass.
Important consecutive changes take place during the process of growth of fibroid. So long as the structure retains its original hard ness, the increase is comparatively slow, con sisting in a simple and uniform multiplication of the elements already described. Occasion ally an increase of density is produced by cal cification of certain portions of the mass, and in this way the so-called bony tumours of the uterus are formed. Or, on the other hand, under rapid growth, the tumour may become softer, in consequence of serous infiltration into its tissues ; the fluid occasionally collect ing in the centre of the tumour and forming there a species of dropsy. Or, a process of inflammation being set up, suppuration, and sometimes sloughing, result. In the more vascular fibroids the vessels may dilate and burst, and the tumour then becomes infiltrated with extravasated blood. It has been doubted whether fibroid ever undergoes absorption. I have reason to think, from occasionally wit nessing a marked diminution in bulk, that this may sometimes occur. The explanation of this is indeed easy when the mass of the tumour consists of hypertrophied muscular tissue, which in such cases has been found to undergo fatty degeneration, and so its disper sion may be effected.
Subperitoneal and interstitial fibroid, when extensive, interferes with pregnancy, and also renders labour difficult or perilous, by weaken ing the expulsive power of the uterus and pre disposing the organ to rupture. Submucous fibroid, in the form of polypi, may prevent impregnation or shorten gestation. In the unimpregnated uterus, all forms, but e.specially the submucous and interstitial, are apt to be accompanied by severe recurrent hwmorrhage, producing excessive anxmia and occasionally death.