666 DISEASES CAUSED BY FILTRABLE VIRUS 



lishing a clew to the mode of contagion among human beings. The same 

 authors, as well as Flexner and Lewis, were able to show that the virus 

 was preservable under glycerin for as long as ten days and retained its 

 virulence for from seven to eleven days when dried. 



According to Flexner and Lewis the virus remains active, when 

 frozen, for as long as forty days, but is extremely sensitive to heat, 

 Uling destroyed by a temperature of from 45 to 50 C. maintained for 

 thirty minutes. 



Experiments aimed at the isolation or even morphological detection 

 of a parasite in the virulent material have been entirely without success 

 until recently. Bacteria which in the past have been isolated from 

 nerve substance and spinal fluid in cases of poliomyelitis can of course 

 be excluded from etiological significance by the recent determination of 

 the filtrability of the virus as determined by Flexner and Lewis, and 

 Landsteiner and Levaditi. Small coccoid forms in smears from the 

 nerve tissue recently described by Proescher 1 are of very uncertain 

 significance. The streptococci recently described by Rosenow are, in 

 our opinion, secondary invaders. The most important contribution 

 which has been made in the solution of this problem is that of Flexner 

 and Noguchi. 2 These investigators placed small bits and emulsions of 

 the brain of monkeys, dead of poliomyelitis, in high tubes containing 

 human ascitic fluid together with a piece of fresh sterile rabbit kidney. 

 In all essentials the method was that followed by Noguchi in his culti- 

 vation of Treponema pallidum. It was necessary to use fresh unheated 

 ascitic fluid. Heat sterilization rendered it unsuitable. 



By this method, after five days opalescence appeared about the 

 pieces of tissue. This increased until the tenth day, when sedimenta- 

 tion began. Microscopical examination by Giemsa's method of stain- 

 ing revealed small globoid bodies measuring from 0.15 to 0.3 micron in 

 diameter, arranged in pairs, short chains, and masses. Similar bodies 

 could later be found in poliomyelitis tissues. Cultures were obtained 

 from glycerinated as well as from fresh virus and from the filtered as 

 well as the unfiltered material. Typical lesions and death have been 

 produced in monkeys with such cultures in a few cases. 



We have few data which throw light upon possible immunity to the 

 disease. Repeated attacks of the disease in the same human being 

 have not been noted ; but this, as Flexner and Lewis point out, may 

 be due to the fact that the epidemics are rare, and individuals once 



1 Proescher, N. Y. Med. Jour., 1913. 



2 Flexner and Noguchi, Jour, of Exp. Med., xviii, 1913. 



