846 THE FILTRABLE VIRUSES 



Prophylactic vaccination. Levaditi and Landsteiner by applying Pasteur's 

 method of vaccination against rabies have successfully vaccinated monkeys 

 against acute anterior poliomyelitis. Infected spinal cords are dried in 

 bottles over caustic potash for varying periods of time (3-9 days) and inocula- 

 tions of emulsions of the dried cords are made at short intervals. 1 



The method is however hardly safe for practical purposes because a cord 

 dried for 24 days over caustic potash still contains the living virus (vide 

 supra). 



Flexner and Lewis have immunized monkeys by inoculating them sub- 

 cutaneously with diluted emulsions of the virus gradually increasing the 

 amount of virus inoculated. 



Though immune serums have been proved to be microbicidal in vitro they 

 have no effect on the course of the disease when inoculated intra-peritoneally 

 or intra-spinally. 



.^Etiology. Flexner is of opinion that in man the nasal mucous membrane 

 is the site both of ingress and egress of the virus of poliomyelitis and from 

 experiments devised to determine the channel of infection " the conclusion 

 is unavoidable that the virus ascends by the nerves of smell to the brain, 

 multiplies in and about the olfactory lobes and in time passes into the cerebro- 

 spinal liquid which carries it to all parts of the nervous organs " (Flexner). 

 The distribution of the virus as spray in coughing and speaking is readily 

 accomplished and by this means both active cases and passive carriers may 

 be produced. 



With regard to other conceivable modes of propagation it is of interest to note 

 that Rosenau, whose observations have been confirmed by Anderson and Frost, 

 has succeeded in conveying poliomyelitis from an infected monkey to other monkeys 

 by means of the bites of flies (Stomoxi/s calcitrans) but as Flexner points out the 

 experiment awaits convincing application to the circumstances surrounding infection 

 in human cases of the disease. 



Seeing that paralysis is not uncommonly observed in dogs, hens and certain other 

 animals, it has been thought possible that some of the lower animals may act as a 

 reservoir of the infection. So far as experimental evidence has been obtained it 

 rather negatives the hypothesis of a relationship between poliomyelitis in man 

 and paralysis in the lower animals. These experiments " do not, of course, exclude 

 the possibility that a reservoir for the virus may exist among domesticated animals 

 that do not even respond to its presence by developing paralysis or other conditions 

 which could be recognized as resembling poliomyelitis in man " (Flexner). 



Diagnosis of anterior poliomyelitis. In mild or atypical cases of the disease 

 which have recovered but in which the diagnosis remains uncertain informa- 

 tion as to the true nature of the disease can be obtained by mixing some 

 serum from the patient with the virus in vitro and inoculating an animal : a 

 control animal being inoculated with the same dose of the virus unmixed 

 with serum. 



Acute anterior poliomyelitis and rabies. In many respects the viruses of these two 

 diseases bear a close resemblance to one another. Thus they both travel along the 

 nerve trunks, both exhibit a selective affinity for the central nervous system, both 

 pass through porcelain or similar filters and both react to chemical and physical 

 influences in a similar manner. These resemblances led Levaditi and Landsteiner 

 to investigate whether an attack of one disease would immunize an animal against 

 the other and were able to show that monkeys highly immunized against anterior 

 poliomyelitis were quite as susceptible to rabies as control animals. 



1 Levaditi and Landsteiner, Ann. Inst. Pasteur, xxiv. p. 866. 



