Here, then, we have a clear and adequate physical basis for appendicitis. A small, twisted, shriveling spur or side twig of the intestine, opening from a point which has become a kind of settling basin in the food-tube, its mouth gaping, as it were, to admit any poisonous or irritating food, infectious materials, disease-germs, the ordinary bacteria which swarm in the alimentary canal, or irritating foreign bodies, like particles of dirt, sand, hairs, fragments of bone, pins, etc., which may have been accidentally swallowed. Once these irritating and infectious materials have entered it, spasm of its muscular coat is promptly set up, their escape is blocked, and a violent inflammation easily follows, which may end in rupture, perforation, or gangrene. Not only may any infection which is sweeping along the alimentary canal, thrown off and resisted by the vigorous, full-sized, well-fed intestine, find a point of lowered resistance and an easy victim for its attack in the appendix, but there is now much evidence to indicate that the ordinary bacteria which inhabit the alimentary canal, particularly that first cousin of the typhoid bacillus, the colon bacillus, when once trapped in this _cul-de-sac_, may quickly acquire dangerous powers and set up an acute inflammation. It is not necessary to suppose that any particular germ or infection causes appendicitis. Any one which passes through, or attacks, the alimentary canal is quite capable of it, and probably does cause its share of the attacks. Numerous attempts have been made to show that appendicitis is particularly likely to follow typhoid fever, rheumatism, influenza, tonsilitis, and half a dozen other infectious or inflammatory processes. But about all that has been demonstrated is that it may follow any of them, though in none with sufficient frequency or constancy to enable it to be regarded as one of the chief or even one of the important causes of the disease.