Note 709 — Chapter XIII · IMMUNITY OF THE SKIN AND MUCOUS MEMBRANES

Perhaps the intestinal micro-organisms also play a part in the immunity of the animal against Entozoa. Many of the examples of this immunity are very striking. Certain intestinal worms can live only in the digestive canal of a single or of a very small number of species of animals. When we feed rabbits with a quantity of the cysticerci of the pig these pass living into the small intestine and are there transformed into true scolices. But, instead of reproducing themselves, they are expelled and never give rise to the development of taeniae. The immunity against intestinal parasites has never been made the object of special study, and it is only as a pure hypothesis that I offer this suggestion as to the part played by the micro-organisms of the intestinal flora.