In The Journal, July 7, I reported briefly my success in transmitting Rocky Mountain spotted fever to the guinea-pig and monkey. With these results in hand, it at once became apparent that a means had been provided by which to test the theory of transmission by the wood-tick, a theory which was primarily advanced by Wilson and Chowning. It was my first aim to establish, beyond the opportunity of doubt, the susceptibility of the animals mentioned, and it was only after this susceptibility had been determined by inoculation from two different patients that the study of the tick as an intermediate host for the parasite was taken up.
On June 19 a small female tick was placed at the base of the ear of "Bradley" Guinea-pig 1. This guinea-pig had been inoculated intraperitoneally on June 11 with three cubic cm. of defibrinated blood from the patient, Bradley, and died with