be performed when the disease is in its incipient state, for then only can success be expected. Exostoses need not to be interfered with, unless they are the source of much inconvenience, either from their size and form, or from their having been detached, and lodged amongst the adjacent soft parts. If loose, they can be removed in the same way as any other extraneous body; if firm, their attachment must be divided by a saw, or by cutting pliers, close to the bone from which they spring. Sometimes, as in the scapula or other flat bone, a portion of the original bony tissue can be cut out along with the new growth, and this renders the chance of any return of disease much less likely. Osteo-sarcomatous tumours are to be taken away, along with the part of the bone in which they are imbedded, and, if possible, before the integuments have ulcerated. The incisions must be made, and the bone sawn, at a healthy part. The removal of the entire bone in which the disease has commenced, when practicable, will afford a still better chance of immunity from farther disease. In spina ventosa more is seldom required than to lay open the cavity, give vent to the matter, and then treat the case on the same principles as in abscess of the soft parts. The cellular tumours, partly cartilaginous, partly osseous, ought not to be permitted to remain; the operation can generally be done without much difficulty; and thus the danger of their degenerating avoided. Frequently, however, a considerable part of the bone must be removed along with the tumour, since the neighbouring tissue is generally softened, and intimately adherent to the diseased part, which it somewhat resembles in structure. In general, regular dissection is unnecessary in the removal of encysted tumours. An incision is made, or an elliptical portion cut out; the contents escape, and the cysts, being then laid hold of by dissecting forceps, is readily separated. In some situations, as on the eyelids, under the tongue, or amongst tendons, the sac, which is thin, is not so easy of extraction; it is then inseparable, either naturally, or from previous inflammation. Caustic is used with safety to destroy those parts which cannot be detached, and for this purpose the potass is to be preferred. When, however, the tumour is large, a part of the integuments covering it must be removed, otherwise a large cavity will be left, in which pus might accumulate. In this case, the base of the tumour is to be surrounded by two elliptical incisions, and the cyst dissected out entire, leaving only integument sufficient to cover the exposed surface. In the smaller tumours, it is vain to attempt regular dissection; a portion of the cyst will be left, and the disease reproduced: whereas, by using the potass, the operation is much more speedy, and always successful. The making a minute aperture, and squeezing out the contents, is at best but a palliative measure, and is often followed by severe constitutional disturbance.