For a long time the supposed best answer to this question was that the vital resistance of the stomach prevented it digesting itself. This theory has been disproved by the fact that the extremities of various reptiles and animals have been introduced into the stomachs of living animals and there acted on by the digestive fluids. Why does the tapeworm, for example, live and thrive in man? An answer may be that this is its natural environment. Prof. Wein-land has shown that this resistance in the tapeworm is caused by certain of what he calls antibodies, analogous to antilysins and antitoxins. He isolated from the tapeworm an antitrypsin or anti-ferment, which when added to a mixture of fibrin and pancreatic juice prevented the digestion of the tapeworm. He also showed the presence of an antipepsin in the secreting cells of the stomach and of an antitrypsin in the cells of the intestines.

These antiferments neutralize the action of the digestive ferments and prevent their destructive action on the tissues of the stomach and intestines. This action, Weinland claims, solves the problem, and is the reason why the stomach does not digest itself.