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SCIENCE 



[N. S. Vol. XLIV. No. 1125 



to make futile the employment of ordinary 

 bacteriological tests for its detection. 

 Nevertheless, the virus can be detected by 

 inoculation tests upon monkeys, which ani- 

 mals develop a disease corresponding to in- 

 fantile paralysis in human beings. In this 

 manner the fact has been determined that 

 the mucous membrane of the nose and 

 throat of healthy persons who have been 

 in intimate contact with acute cases of 

 infantile paralysis may become contami- 

 nated with the virus, and that such con- 

 taminated persons, without falling ill 

 themselves, may convey the infection to 

 other persons, chiefly children, who develop 

 the disease. 



Relation of Virus to Types of the Disease 

 The virus has, apparently, an identical 

 distribution irrespective of the types or 

 severity of cases of infantile paralysis. 

 Whether the cases correspond with the so- 

 called abortive forms of the disease in 

 which definite paralysis of the muscles does 

 not occur at all, or is so slight and fleeting 

 as often to escape detection; whether they 

 correspond with the meningeal forms in 

 which the symptoms resemble those of 

 acute meningitis with which muscular 

 paralysis may or may not be associated ; or 

 whether they consist of the familiar para- 

 lytic condition, the virus is present not 

 only within the nervous organs, but also 

 upon the mucous membranes of the nose, 

 throat and intestines. 



Escape of the Virus from the Body 

 Microorganisms which convey disease 

 escape from the body of an infected indi- 

 vidual in a manner enabling them to enter 

 and multiply within fresh or uninfected 

 individuals in such a manner as to cause 

 further disease. The virus of infantile 

 paralysis is known to leave the infected 

 human body in the secretions of the nose, 

 throat and intestines. It also escapes from 



contaminated healthy persons in the secre- 

 tions of the nose and throat. Whether it 

 ever leaves the infected body in other ways 

 is unknown. At one time certain experi- 

 ments seemed to show that biting insects 

 and particularly the stable fly might with- 

 draw the virus from the blood of infected 

 persons and inoculate it into the blood of 

 healthy persons. But as the virus has 

 never been detected in the blood of human 

 beings and later experiments with the 

 stable fly have not confirmed the earlier 

 ones, this means of escape of the virus must 

 be considered doubtful. On the other 

 hand, it has been shown by experiments on 

 animals, so that the same facts should be 

 regarded as applicable to human beings, 

 that the virus seeks to escape from the 

 body by way of the nose and throat, not 

 only when inoculation takes place through 

 these membranes, but also when the inocu- 

 lation is experimentally made into the ab- 

 dominal cavity, the blood, or the brain 

 itself. From this it is concluded that the 

 usual means of escape of the virus is by 

 way of the ordinary secretions of the nose 

 and throat and, after swallowing these, with 

 the discharges of the intestines. 



Entrance of the Virus into the Body 

 The virus enters the body, as a rule if 

 not exclusively, by way of the mucous 

 membrane of the nose and throat. Having 

 gained entrance to those easily accessible 

 parts of the body, multiplication of the 

 virus occurs there, after which it pene- 

 trates to the brain and spinal cord by way 

 of the lymphatic channels which connect 

 the upper nasal membrane with the interior 

 of the skull. Whether the virus ever enters 

 the body in any other way is unknown. 

 Certain experiments already alluded to 

 make it possible that it may be inoculated 

 into the blood by insects, and other experi- 

 ments have shown that under peculiar and 

 extraordinary conditions, it may in mon- 



