A mechanical factor of great importance also exists in the spontaneous collapse and automatic apposition of the walls of the track. This closure is rendered additionally effective in many cases by the interruption of the continuous line in the wounded tissues consequent on alteration in the position of the parts traversed when an attitude of rest is assumed by the injured part. The indisposition to suppuration and the apparent unsuitability of the tissue lining the track for the development and spread of infecting organisms are well illustrated by several observations. Thus, even if the bullet be thoroughly aseptic, the fragments of destroyed skin driven into the track by the bullet can scarcely be free from organisms; yet these seldom give rise to trouble. Again, if for any reason a deep portion of a track becomes infected and suppurates, there is no tendency for the spread of infection along the line of wounded tissue, but rather for the development of a local abscess, pointing in the ordinary direction of least resistance, irrespective of the course originally taken by the bullet. [Illustration: PLATE I. Engraved and Printed by Bale and Danielsson, Ltd. G. L. CHEATLE. Mauser Wound of Entrance, a little more than 48 hours after infliction. About 12/1. Section of the entry segment of an aseptic Mauser wound removed a little over forty-eight hours after its infliction. Magnified twelve diameters. The margins of the opening are still sloping and depressed, indicating the originally 'punched-in' nature of the aperture. A thin stratified layer of epidermis completely closes it. No scab remains. The wound track is occluded by an effusion of lymph, commencing organisation of which is shown under a higher magnifying power by the presence of leucocytes near the margin of the bounding tissue, and some giant cells. The effusion of lymph occupies a slightly wider area immediately beneath the papillary layer of the skin, then narrows, and broadens again as the subcutaneous fascia is reached, indicating the effect of resistance in widening the area of damage. The subcutaneous connective tissue bounding the track shows little sign of alteration beyond a general slight tendency of the lines of structure to deviate in the direction of the passage of the bullet. No haemorrhage is apparent beyond a small collection of blood situated immediately beneath the new layer of epidermis at the left-hand corner of the opening. Range probably within 800 yards. Seat of wound, abdominal wall a highest point of iliac crest.]