Abstract
Ultrafiltration studies on so-called filterable viruses, including fowl-plague, vaccinia, herpes, foot-and-mouth disease and mosaic diseases of plants, have been reported by Andriewsky, 1 Doerr and Pick, 2 Levaditi and Nicolau, 3 Duggar and Karrer-Armstrong, 4 Levaditi, Nicolau and Galloway, 5 Olitsky and Boëz, 6 Zinsser and Tang, 7 Berger, 8 but to our knowledge no such investigations have thus far been reported on the virus of poliomyelitis. While the filterability of this virus through Berkefeld candles has been reported (Landsteiner and Levaditi, 9 Flexner and Lewis 10 ) it is still not known whether the etiological agent is a small bacterium or a true ultrascopic virus. With this in mind we have undertaken a program of investigation designed to elicit more accurate information as to the magnitude of the organism concerned. The present paper deals with some of our observations thus far.
Our experiments were carried out with a highly virulent strain of poliomyelitis virus (Aycock strain). The virus suspensions were prepared by grinding the recently harvested cord and medulla of poliomyelitis monkeys in a mortar,† in the presence of quartz sand, for at least one hour. The material was then made up into a 5% suspension in neutral physiological saline. Before filtration the suspensions were centrifuged at moderate speed for 5 to 15 minutes to remove the larger particles. The reaction of the suspension after centrifugation was then determined by a colorimetric method and was found to be between pH 5.80 and pH 5.90.
The membranes through which the suspensions were filtered were prepared by dipping Whatman No. 1 filter paper into glacial acetic acid containing various percentages of dried Anthony's negative cotton.
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