_Calibre._--The effect of the diminution of calibre is (_a_) to reduce the area of impact of the bullet on the part impinged upon, and hence to lower the degree of resistance offered by the tissues; this to a certain extent tends to neutralise the augmented striking force resulting from the increased velocity of flight. (_b_) To limit considerably the destructive powers of the bullet, as a smaller area of tissue is exposed to its action. (_c_) To allow of the production of very 'neat' injuries and the frequent escape of important structures, also the production of remarkably prolonged subcutaneous tracks in positions where such would be regarded as scarcely possible, and in point of fact were impossible with the older and larger projectiles. _Length._--The comparative increase in length of the bullet is, from the surgical point of view, only of material importance in increasing the weight and therefore the striking power, and in so far as it is a mechanical necessity for the flight of the projectile on an axis parallel to its long diameter, and so tends to ensure impact on the body by the tip of the bullet. This latter is, however, surgically favourable as ensuring a smaller wound. _Weight._--The decrease in weight must be regarded on the whole as altogether to the advantage of the wounded individual, since it cannot be considered to be entirely compensated for by the resulting increased velocity of flight, unless the range of fire is moderately close. _Shape._--The ogival tip and general wedge-like outline, while decreasing the aerial resistance to and increasing the power of penetration possessed by the bullet, at the same time allow the escape of some structures by displacement, while others are saved from complete destruction by undergoing perforation. Beyond this the sharper the tip, the smaller is the area of the body primarily impinged upon, the less the resistance offered to perforation, and to some degree the less the destruction of surrounding tissues. _Increased velocity of flight._--This multiplies the striking force, and compensates in part for decrease in volume and weight of the bullet. It is customary to speak of the velocity as 'initial' and 'remaining.' Initial velocity is the term employed to express the velocity at the time of the escape of the bullet from the barrel; this is also designated as 'muzzle velocity.' 'Remaining velocity' expresses that obtaining during any subsequent portion of the flight of the projectile.