INDIAN FORM OF RELAPSING FEVER. 191 



When I fiuall}' reached Bombay with m}^ animals, I was unable to find 

 any cases of relapsing fever there. Only jnst before my departure from 

 that city several cases occurred in the Hospital for Infectious Diseases, 

 presided over by Doctor Choksy. However, these cases were evidently in 

 a stage of relapse and their blood was of no value for experimental pur- 

 poses. As my sup]:)ly of -wliite mice was by this time exhausted, my 

 experiments in relation to the Indian form of relapsing fever would have 

 failed but for the timely assistance of Captain Mackie of the Indian 

 Medical Service of Bombay. Fortunately I had secured in Egypt through 

 the kindness of Dr. Keating(3, director of the Cairo School of Medicine, 

 some white rats which, during the voyage to India, I had immunized 

 against tlie different s])irocha3ta\ At my reqiiest, Captain Mackie kindly 

 consented, when a fresh case of the Indian disease should occur, to 

 attempt to infect with the Indian spirillum my rats which had been 

 immunized separately against the African (Koch and Dutton strains), 

 European and Amei'ican strains of spirocliEeta^. Each animal had been 

 highly immiuiized with one of these strains by repeated injections of 

 blood containing the spirochgeta in c|uestion and the animals were no 

 longer capable of being infected with the respective organisms. Captain 

 Mackie was unable to obtain suitable blood containing the Indian species 

 of spirocha^ta until forty-eight days after my last injection of the rats 

 with the spirochsetaj, at this time, however, the attempt was made to 

 infect them. As immunity in such animals has been shown to persist 

 for many months by Novy, Manteufel and myself, they were evidently 

 still immune to the strain with which they had been previously inoculated 

 at the time the attempt to reinfect them was carried out by Doctor Mackie. 

 The rats were all inoculated with about 0.4 cubic centimeter of pure blood 

 in citrate solution. The blood at the time of the inoculation contained 

 numerous actively motile spirochajtse. All of the injections were made 

 intraperitoneally. Control, normal rats were also inoculated at the same 

 time. Twenty-four hours after the injections were made a microscopic 

 examination of the blood of the animals showed that no spirochsetaj were 

 present in those immunized with the American and with the European 

 strains, but that spirochsetfe were present in the blood of all those animals 

 immunized against the African strains as well as in the blood of the 

 control normal animals. Forty-eight hours after infection the spiro- 

 ch^tfe were still present in the blood of one' of the animals immunized 

 against the African species, and, as might be expected, in one of the 

 control, normal animals; in all of the others the spirochsetae had disap- 

 peared. An examination seventy-two hours after infection showed the 

 blood of all the animals negative for parasites and the organisms did not 

 appear or reappear again in any, as was evidenced by repeated careful 



examinations. I take this opportunity publicly to tliank Captain Mackie 

 86321 4 



