In many encysted tumours, hairs grow from the internal membrane of the cyst, often numerous, and are generally found in those situated on the eyelids; in some the hairs are destitute of bulbs, lie loose within the tumour, and are often rolled into a globular form. The adhesions of these tumours are in general very slight and easily broken up, but when seated amongst tendons, or in unyielding parts, they are often extremely firm. Violent inflammatory action may follow injuries of the tumours, or the making of even minute openings into them; suppuration occurs, the discharge is thin, fetid, and often bloody; there is much pain, and frequently severe constitutional irritation. Occasionally a fungus, bleeding or not, is protruded through the aperture; more frequently, however, the opening heals, and the tumour remains as before. External injuries sometimes appear to check the secreting action, and to excite the absorbents to remove the morbid growths, and this with or without rupture of the cyst. Thus, in the case of an encysted tumour the size of a hen’s egg, on the external lateral ligament of the knee joint, free and pretty rough manipulation was necessary to ascertain its nature and exact situation; in consequence of which, the tumour gradually disappeared, and no traces of it remained twelve days afterwards. Others of less size, I have known to disappear in a much shorter period. OF TUMOURS OF BONES. The vascular action of bones, in their healthy state, is feeble, but, as in other feeble parts, it is easily excited, and disease of an obstinate and unyielding nature is apt to follow. The morbid growths vary much in texture. The most frequent are the osseous, or those of the same structure with the original bone; but even these differ much in the density and arrangement of their particles: they have been termed _exostoses_. They may be of great density, and are then called the hard, or ivory; these never attain a large size, seldom exceed that of a bean, have a smooth and polished surface, and are of a flattened and hemispheroidal form, their greatest circumference being at the base; they occur in many of the bones, but generally in those of the cranium and face.