262 DISCUSSION.
subcutaneous injection of blood or serum withdrawn during the first twenty-four hours of the patient's illness caused fever nineteen times."
I should like to ask Lt.-Col. Birt, what was the total number of cases ?
Lt.-Col. Birt : Every case was successful. No rashes, except the efifects of biting insects, have been observed in the Maltese, Cretan, Italian, or Chitral epidemics of phlebotomus fever ; but we meet with many cases of dengue in which skin eruptions are absent, and the general pains are not severe. As, moreover, the pyrexia may last three or four days only, such attacks of dengue are indistinguishable from phlebotomus fever.
With regard to the filtration of the virus, in the experiments carried out in Malta, 5 c.c. of blood were mixed with 45 c.c. of sterile physiological salt solution before clotting had taken place. The mixture was placed immediately in a Cobbett's filter fitted with a " Chamberland F. candle controU^." Filtration was conducted very slowly under the pressure of gravity only, at a temperature of 78° F. Twenty-four hours elapsed before 20 c.c. of filtrate had collected. The filtrate contained no microscopical elements, and was sterile on culture. The reliability of the candle was tested, before and after use, with emulsions of the M. melitensis, which was retained on both occasions, hence no protozoa were present in the filtrate.
Though it has not been ascertained with certainty how the virus of phlebotomus fever is preserved during the winter, and how the epidemics of phlebotomus fever are bridged over, Doerr has adduced evidence that there is hereditary transmission of the virus from phlebotomus to ovum and larvae, and thence to the mature fly. The question could be answered by emulsifying the ova of infected phlebotomi, filtering the emulsion through a porcelain candle, and injecting the filtrate into U susceptible subject.
