THE FILTERABLE MICROBES • 393 



by the injection of serum from a hyperimmune hog (passive 

 immunity) and by the injection of such serum together with viru- 

 lent blood from a hog sick with the disease (combined passive 

 and active immunity). 



The Virus of Dengue Fever.^ — Ashburn and Craig showed in 

 1907. that the virus of this disease exists in the blood of the pa- 

 tients and that it is filterable. The disease is probably trans- 

 mitted by the mosquito Culex fatiga/ns. Apparently the analogy 

 to yellow fever is rather close. 



The Virus of Phlebotomus Fever. — Doerr in . 1908 demon- 

 strated a filterable virus in the blood of persons suffering from 

 the benign three-day fever of Malta and Crete. The disease is 

 rather widely distributed in tropical countries. It is transmitted 

 by the sand-fly Phlebotomus papatasii.^ 



The Virus of Poliomyelitis. — Several investigators, among 

 them Flexner and Lewis, demonstrated in 1899 the presence of a 

 filterable virus in the central nervous system of patients suffering 

 from infantile paralysis. The virus also occurs in the nasal mucus 

 and in the blood. It survives in glycerine for a month, also re- 

 sists freezing for weeks, and is rendered inert at 45° to 50° C. in 

 30 minutes. It is quickly destroyed by hydrogen peroxide and 

 by menthol. 



Flexner and Noguchi^ have obtained cultures of the organism 

 in ascitic fluid containing sterile tissue and covered with paraflin 

 oil, and in this medium rendered solid by admixture of agar. 

 The colonies are made up of minute globose bodies 0.15 to 0.30;^ 

 in diameter. Similar bodies have been identified in the nervous ■ 

 tissue from cases of the disease. It seems probable that this 

 structure is a living organism and the microbic cause of poliomye- 

 litis, especially as inoculation of monkeys with the cultures has 

 given rise to the disease. Flexner and his coworkers' regard this 

 ' Brit. Journ. Roy. Army Med. Corps, XIV, pp. 1920, Vol. 236-258. 

 ' Journ. A. M. A., 1913, V. LX,p. 362. 



'Amoss, H. L.: Survival of poliomyeUtic virus in brain of rabbit, Journ. Exp. 

 Med., 1918, 27, p. 443; Smillie, W. G., Cultivftion exp'eriments on globoid bodies^of 

 poliomyelitis, ibid., 1918, 27, p. 319. 



