It has hitherto been firmly established from experience gained in the studfarms and by experimental investigations (Hertwig, Prince and Lafosse, Frasbot, Pench) that Dourine is transmitted almost exclusively through coitus. Flies take no part in the transmission of the disease (Laveran and Mesnil), however, the possibility of infection through the bite of fleas (Eabino-witsch and Kempner) or ticks, is not excluded, and was proved experimentally (Sieber and Gonder). Experiments conducted on rabbits and dogs (Rouget, Schneider and Buffard, Laveran and Mesnil) have shown that T. equiperdum is capable of penetrating through the intact mucous membrane of the eye and genital organs, but not through the alimentary tract. Manteuffel's experiments have shown that T. equiperdum can even penetrate through the intact skin.