With the fissures and the large splinters, which we need not describe again, there is an orifice in the bone, generally rounded in shape, sometimes oval whose diametrical dimensions are less than those of the bullet. The bony aperture of entry is circular and regular, of the same dimensions as the projectile, or smaller, occasionally oval in shape. The bony aperture of exit is variable in form. In such an instance the bullet has not acted alone, as in a contact fracture or in perforation of only one bony wall. The splinters it has torn off at the aperture of entry, the subdivided splinters close to the track to which the bullet has communicated part of its active power, the fragments of the bullet which may have broken in pieces, have all acted as secondary projectiles .
Grooves generally affect but a very small extent the transverse diameter of the bone.
We must differentiate the grooves of the ridges from those of the body of the diaphyses. Grooves of the Sides and of the Ridges of the Bone . As the bone, in the tangential contact that precedes the abrasion causing a groove, cannot have received a shock from active force as intense as the one it would experience when struck point-blank, which would lead to perforation, the groove may generally be placed in the type in which there is little or but slight comminution . This is an important fact. It results from this that a great many grooves exist without any solution of continuity of the bone.