The ordinary house fly conveys in this way the organisms of typhoid and dysentery.

Flies seek the discharges not only for food, but for the purpose of depositing their eggs, and the hairy and irregular surface of their feet facilitates contamination and conveyance.

When flies eat such discharges the organisms may pass through the alimentary canal unchanged and be deposited with their feces; they also often vomit or regurgitate food, and in this way also contaminate objects.

Flies very greedily devour the sputum of tuberculous patients, and the tubercle bacilli contained in this pass through them unchanged and are deposited in their feces.
[Illustration: FIG.

19 .-- TRYPANOSOMES FROM BIRDS.