COG DISEASES CAUSED BY F1LTRABLE 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, 

 being 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 clouding of ascitic fluid after an incubation with 

 poliomyelitis nerve substance has been found to be due to protein pre- 

 cipitation. The most important contribution which has been made in 

 the solution of this problem is that of Flexner and Noguchi. 2 These in- 

 vestigators placed small bits and emulsions of the brain of monkeys, 

 dead of poliomyelitis, into 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 cultivation of Treponema 

 pallidum, except that in the case of poliomyelitis anaerobic pus was 

 unnecessary. It sufficed to cover the ascitic fluid with a layer of sterile 

 alboline. 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 pro- 

 duced in monkeys with such cultures even after the eighteenth genera- 

 tion on artificial media. 



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



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



