EPIDEMIC POLIOMYELITIS 645 



In animals other than monkeys no result followed infection. A 

 raivful microscopic examination of the nervous system in natural 

 and experimental cases did not disclose the presence of bacteria 

 or protozoa, and it was found that the virus could pass through 

 a llrrkefeld lilter without losing its infectivity, and that the cords 

 of animals thus infected were still infective for further animals, 

 men- toxic action being thus excluded. These results have been 

 continued by Levaditi working with the chimpanzee, and then- is 

 thus little doubt that here again we are dealing with an ultra- 

 micruscnj.ic vims. Flexner found that when the virus was 

 mixed with bouillon a turbidity developed, but no formed 

 organic body could be detected. He further found that monkeys 

 which had passed through the illness following inoculation \\ere 

 insusceptible to re-inoculation, and both he and Levaditi noted 

 that the serum of such insusceptible, monkeys had the capacity 

 of neutralising the virus, a similar result being obtained with 

 the serum of human cases which had recovered. 



With regard to the distribution of the virus in an infected 

 animal, the chief concentration is found in the nervous system, 

 but it was also found in lymphatic glands ; as has been stated, 

 the cerebro-spinal fluid is apparently inert. No facts are known 

 bearing on the channel of natural infection or on the path by 

 which the poison reaches the cord, whether by the general 

 lymph stream or by the sheaths of nerves, but the virus can 

 be eliminated by the nose, 'and infection can also be effected 

 through the scarified nasal mucosa. In its pathology the 

 condition bears many resemblances to rabies. 



These recent observations are of the greatest importance in 

 relation to the etiology of the condition and also possibly in 

 relation to treatment. 



