The louse infesting jack rabbits _Haemodipsus ventricosus_, can transmit the infection from rabbit to rabbit so that the infection in the jack rabbits is probably kept up by this agency. Recent experiments have shown that the infection in white mice can be transferred by the bites of the mouse louse and also by bedbugs. Again if the mice are fed on infected bedbugs transmission is found to take place by such feeding experiments. The faeces of such bedbugs prove infectious. Guinea pigs injected subcutaneously with the urine of white mice suffering from the disease die acutely with typical lesions of tularaemia. Mice fed on the liver of a rabbit dying of the disease succumbed to the infection within five days. As noted under etiology the most important method of spread of the disease to man is by the bite of an infected horsefly (_Chrysops discalis_). From experimental studies it would seem that any biting arthropod might prove a transmitting agent. In view of the fact that the infected deer fly tends to lose its infectivity after about five days Francis is of the opinion that the fly is only a mechanical transmitter of the organism. Wherry reported the infection as manifested by conjunctivitis with glandular involvement and due to handling infected wild rabbits. Lake and Francis have reported that of six investigators from the Hygienic Laboratory working with this infection all have contracted the disease. There were fortunately no fatalities. Such an experience demonstrates the great infectivity of this virus and must lead to the conclusion that the few cases so far reported of the disease do not represent the importance of tularaemia in man. With a knowledge of the existence of such an infection and with satisfactory methods of laboratory diagnosis we shall probably have other reports of the infection. We now know that the ground squirrels of California and Utah, the jack rabbits of Utah and the wild rabbits of the middle west furnish important reservoirs of virus. PATHOLOGY In experimental animals we have lesions which cannot well be differentiated from those of plague. There is not sufficient data for a statement as to the pathology in man. In experimental animals we have a definite bacteriaemia but in man the organism has only in rare instances been obtained from the blood. SYMPTOMATOLOGY It has been difficult to determine the period of incubation but in one laboratory infection the disease set in seven days after the patient began tularaemia work. There do not seem to be any prodromata. [Illustration: FIG. 71.—Temperature chart of a case of laboratory infection (tularaemia.)]