ACUTE ANTERIOR POLIOMYELITIS 845 



relied upon to infect the animal. Infection follows if the virus be inoculated 

 into the sheath of a nerve trunk ; this is of interest in that it shows that the 

 virus travels up the nerves, probably along the lymphatics. 



Further, after inoculation of the virus into a nerve trunk the characteristic 

 paralyses always appear first in the limb supplied by that nerve (Flexner 

 and Lewis, Levaditi and Landsteiner, Leiner and Wiesner). 



With regard to infection by the respiratory passages : In their earlier 

 experiments Levaditi and Landsteiner failed to infect monkeys either by 

 painting the mucous membranes of the nose and back of the throat with an 

 emulsion of the virus or by plugging the nasal fossae with wool soaked in the 

 virus, but succeeded when they inoculated the infected material beneath the 

 nasal mucous membrane. Flexner and Lewis also infected animals by 

 painting the virus on the scarified surface of the nasal and pharyngeal 

 mucous membranes. 



Leiner and Wiesner, on the other hand, were able to infect monkeys by 

 painting the nasal mucous membrane without previous scarification, by 

 inhalation and by injecting the virus into the trachea and though Levaditi 

 and Landsteiner suggested as a possible explanation of these results that the 

 monkeys used by Leiner and Wiesner may have had at the time of the 

 experiment some small abrasions on the mucous membranes which escaped 

 their observation, it is now established that the virus passes with readiness 

 and constancy from the intact, or practically intact, mucous membrane of 

 the nose to the central nervous system (Flexner). 



Experimental monkeys have never been observed to contract the disease 

 by contagion (Flexner and Lewis, Levaditi and Landsteiner, Leiner and 

 Wiesner, Roemer). 



Symptoms generally appear after an incubation period of about 8 days 

 (7-11 days). The period of incubation is rather longer when a filtered virus 

 is used than when an unfiltered emulsion is inoculated and also when a 

 relatively small dose is inoculated. 



Symptoms. After the period of incubation has elapsed certain prodromal 

 symptoms of which the most constant are twitchings all over the body mark 

 the onset of the disease. These initial symptoms are followed, as a rule 

 within a few hours, first by paralysis of the hind limbs, then of the posterior 

 part of the body, trunk, arms and neck : the bulbar centres are subsequently 

 affected, and death takes place in 2-3 days. This is the most usual course 

 for the disease to run and is known as the Ascendinci type. It resembles 

 Landry's ascending paralysis often observed during epidemics of acute 

 anterior poliomyelitis. 



In another type known as the superior type the neck muscles are mainly 

 involved and to some extent the muscles of the fore limbs. 



The experimental disease is occasionally manifested by paralysis of the 

 motor cranial nerves, generally the Vllth or the Illrd. 



In addition to these types various " mixed " paralyses may be produced. 



In milder infections the acute symptoms are followed by paralysis, mus- 

 cular atrophy and deformity : occasionally the animals recover completely. 

 In a few cases relapses occur and a different part of the body from that 

 attacked in the first instance may be involved. 



Immunity. One attack of the disease even if atypical and abortive almost 

 always confers a complete and lasting immunity. 



The serum of persons and of experimental animals which have recovered 

 from the disease is microbicidal in vitro (Levaditi and Landsteiner, Flexner 

 and Lewis). 



