Excisions have the special peculiarity and danger of dealing chiefly with cancellated bone, broadened out, open, with numerous patulous canals for large veins, tending on any irritation or inflammation to set up a diffuse suppuration, and to culminate in phlebitis, myelitis, and other pyæmic conditions. Excisions are performed through degenerate or disorganised, amputations through healthy, tissue. Excisions require extreme care and absolute rest (_i.e._ in lower limb) for many weeks and months after the operation. But, on the other hand,-- Amputations remove a portion of the body; excisions a much less one. Amputations are always necessarily nearer the centre than the corresponding excisions, and statistics show that the fatality of operations increases in exact proportion as they approach the centre. A successful excision, especially in arm, saves a limb nearly perfect; an amputation at best is only the stump for a wooden one. On the whole, there is actually very little difference in the mortality of excisions and amputations. 2. As to the results of the operation on the usefulness of the limb, depending on joint involved, age of patient, and amount of bone removed:-- A. _Joint involved._--These must be noticed separately, but one thing is absolutely certain, that a much higher standard of usefulness, both in equality of length, amount of anchylosis, and position, is needed in the lower than in the upper limb. For a leg hanging like a flail, or shortened by some inches, is not so good for purposes of locomotion as a wooden leg is, while an arm, even though powerless at the elbow, and perhaps much shortened, can be so strengthened and supported by slings and bandages as to give a most useful hand, the complex movements and uses of the fingers of which no mechanism can at all imitate. B. _Age of Patient._--It must be remembered that excision in a child removes the epiphyses by which in great measure the growth of the bone is to be managed, and the stunted limb, especially in the leg, will eventually be of little advantage, though after the operation it looked excellently well, if a few years later it be found to be seven or eight inches shorter than its neighbour. C. _Amount of Bone removed._--From an erroneous view of the pathological changes in the bone affected, far too much was removed by many of the earlier operators, especially Moreau and Crampton. The reason that this is often still the case, is well seen in many preparations. The bones are thickened to a considerable distance, and covered with irregular warty excrescences. These, which used to be considered evidences of disease, are only compact new healthy bone, thrown out like the callus of a fracture in consequence of the irritation. In a word, what we require to remove is the following:-- 1. All the cartilage, dead or alive, healthy or diseased.