688 EPIDEMIC POLIOMYELITIS 



has been found that in monkeys recovered from the disease, the 

 nasal mucosa remains infective for many months after the virus 

 has disappeared from the central nervous system, and it has 

 been established that in man there are chronic carriers such as 

 exist in other diseases. As in other conditions, the carrier may 

 not himself suffer from the effects of the infective agent which he 

 carries. Further, the occurrence of abortive cases may con- 

 stitute a means by which infection is maintained in a community. 

 Such abortive cases are probably fairly common during epi- 

 demics. In connection with this aspect of the subject, Amoss 

 and Taylor have made the interesting observation that in some 

 individuals the normal nasal secretion possesses a certain power 

 of neutralising the poliomyelitic virus. Finally, it is to be 

 noted that there is a periodicity in the incidence of poliomyelitis 

 in an epidemic form. As bearing on the explanation of this, 

 Flexner, Clark, and Amoss record- the case of one strain of the 

 virus the virulence of which in monkeys was at first low, and 

 then rose to a maximum which was maintained for three years ; 

 this phase was succeeded by a decrease in infectivity in a few 

 months, without apparent cause. It is obvious that this fact 

 is not only of importance in relation to poliomyelitis, but is 

 suggestive as bearing on the periodicity of other epidemic 

 diseases. 



Some workers differ from Flexner on certain points regarding 

 the pathology of poliomyelitis. Thus Rosenow and Towne look 

 on the "globoid bodies" as specially small forms of a rather 

 large streptococcus which they have isolated from the brain in 

 both the natural and experimental disease, — which can grow 

 under aerobic conditions and can produce poliomyelitis, not only 

 in , monkeys but also in rabbits. These organisms have been 

 found in certain cases by other observers, who, however, deny 

 that the disease conditions they produce are to be classified 

 with poliomyelitis. Another point on which difference of 

 opinion has arisen is regarding the mode of spread of the 

 disease. Rosenau has put forward observations pointing to a 

 blood-sucking fly, stomoxys calcitrans, being capable of trans- 

 ferring the disease in monkeys. As the worst epidemics of 

 poliomyelitis occur in summer, the possibility of an insect carrier 

 has thus been entertained. The absence of the virus from the 

 blood in man, and the difficulty of originating the disease by 

 intravenous injection, are facts militating against such a theory, 

 which, it must be held, has not yet been established. 



Though no cases are recorded of a second attack of poliomyel- 

 itis in man, our knowledge regarding immunity is mainly derived 



