During the course of healing some other peculiarities are worthy of mention. First of all, union was tardy and often not strong. On the other hand, an abundance of provisional callus was common, which formed large swellings apt to implicate neighbouring nerves, and sometimes to interfere with the movements of joints. The slowness of healing was particularly noticeable in those cases where the degree of local shock had been marked, and was probably to some extent dependent on disturbance of the general nutrition of the tissues of the affected limb. Beyond this, however, it was in many cases a direct result of the degree of comminution and displacement of the fragments, which necessitated the formation of a large amount of provisional callus, and time for the proper consolidation and contraction of the same. In many cases a large ball-like mass of callus surrounding the fragments was developed, into which the actual ends of the broken bone only dipped, and hence union was weak and insecure. As to those cases in which the wounds closed by primary union, we must bear in mind in this relation the tardy union often observed in civil practice, when the irritation of suppuration and consequent inflammation are absent. Another peculiarity of a similar nature was the occasional late necrosis of fragments; the wounds apparently healed well, only to break down weeks or months later for the discharge of a sequestrum. Such cases were quite distinct from those in which primary suppuration had occurred. I saw one or two instances in fractures of the humerus, the trouble arising with commencing use of the limb, and I suppose that fragments which suffered death at the time of the injury had been enclosed, and only caused irritation as foreign bodies when the muscles again came into action. In the absence both of evident necrosis and suppuration, however, in some cases the exit portion of the track in the soft parts was extremely slow in healing. Although no discharge beyond a small quantity of blood-tinged serum escaped, the wounds remained open for many weeks, even when the fracture consolidated well. I ascribed this to slow separation of aseptic sloughs, a point which has already been mentioned under the heading of wounds in general. Superabundance of callus, as far as I had an opportunity of judging, comparatively seldom gave rise to permanent mechanical trouble. This was no doubt due to the infrequency of extension of the comminuted fractures beyond the junction of diaphysis and epiphysis.