Several explanations are to hand, but none of them conclusive. Two must, however, be shortly considered. First, the surface of the bullet, except its tip and base, is practically renewed by passage through the barrel. Secondly, there is the question of the heat to which it is subjected. As far as cauterisation of the tissues is concerned, this question has been practically settled in the negative, since actual determinations of the heat immediately after the moment of impact have been made, and again it has been shown that butter is not melted, and that neither gunpowder nor dynamite is exploded, by firing bullets through small quantities of those materials. Again, the absence of any sign of scorching of the clothes of the wounded is strong evidence against the possibility of any considerable heat being applied to the tissues of the body; while another observation, although of less importance as affecting spent bullets only, that bullets, which have perforated the body but lie between the skin and the clothing, leave no sign of cauterising action on either, may be mentioned. None the less, the sources of heating while the bullet is passing from the barrel are many and obvious. Thus there is the heat consequent on explosion of the powder, the warm state of the barrel itself when the rifle has been fired a few times consecutively, and the heat resulting from the force and friction essential to the propulsion of the bullet through the barrel. Again, bullets covered with wax before their introduction into the barrel retain no trace of this when they have been fired, although at any rate the portion covering the tip is not exposed to friction on the part of the rifle, and lastly the base of the bullet has no other explicable reason for its innocuousness than subjection to a certain degree of heat. While not claiming any cauterising action on the tissues by the bullet, I should therefore still be inclined to allow the probability of the heat to which the surface of the bullet is exposed exerting a cleansing action on the projectile. In regard to this point it is interesting to bear in mind that shots from an ordinary gun seldom or never give rise to infection.