if the virus be allowed to dry in thin layers of infected tissues, if it be allowed to desiccate therefore under conditions which approximate to actual experience, it rapidly decreases in virulence. The poison is more sensitive to high than to low temperatures. At 55° C. it loses its virulence, and at 45° C. it is perceptibly attenuated.
Much of the experimental research has been directed towards the question of acquired immunity and many interesting facts have been discovered. Flexner and Lewis, Landsteiner and Levaditi, and Römer and Joseph demonstrated that monkeys which recovered from one infection with the virus of poliomyelitis are immune. According to Joseph and Römer this immunity is present even when the first infection produces no clinical symptoms. Moreover, antibodies can be demonstrated in the blood of such immune monkeys. These antibodies can neutralize the action of the virus in vitro (Römer and Joseph, Landsteiner and Levaditi, Flexner and Lewis). Netter and Levaditi, and Flexner and Lewis have further shown that in the serum of children who have recovered from infantile paralysis, antibodies are present; and Netter and Levaditi have also established that these antibodies can be demonstrated in the abortive forms of the disease. Wollenstein, Römer and Joseph, and others failed, however, to demonstrate the presence of amboceptor (komplementbinden Antikorper) in the cerebrospinal fluid or in the blood serum of patients who were suffering from, or who had recovered from poliomyelitis. From similar investigations on monkeys they obtained negative results. Römer and Joseph call attention to the fact that if in highly immunized animals this absence of amboceptor is shown to occur, the analogy already recognized between poliomyelitis and rabies would be reinforced; for amboceptor has not as yet been demonstrated in rabies.
In has already been stated that no culture has been obtained from the spinal cord. Flexner and Lewis and Levaditi have, however, given us an impulse to the further study of the propagation of the virus outside the body for in bouillon prepared from the clear, bacterial-free, virulent spinal cord filtrate they have seen arise a cloudiness which was not due to any contaminating bacteria. With the aid of Borrel's modification of the Löffler method, Levaditi thought that he further observed in the cloudy bouillon
