The less frequency of infection in modern wars is in part due to the simpler character of the wounds and in part to the fact that modern fixed ammunition is practically free from germs.

The old spear-head, the arrow, the cross bow bolt, had little regard for the probabilities of infection.

Whether infection follows a wound depends both upon the entry of pathogenic organisms and upon these finding in the tissues suitable opportunities for growth.

In wounds in which there is much laceration of tissue organisms find the most favorable conditions for development.

The very slight wounds produced by the exploded cap in the toy pistol give suitable conditions for the development of the bacillus which produces tetanus or lockjaw.