244 Arthropod Transmission of Disease 



The resiilts of these experiments gained much publicity and in 

 spite of the conservative manner in which they had been announced, 

 it was widely proclaimed that infantile paralysis was conveyed in 

 nature by the stable-fly and by it alone. 



Serious doubt was cast on this theory by the results of further 

 experiments by Anderson and Frost, reported in May of 1913. 

 Contrary to the expectations justified by their first experience, the 

 restdts of all the later, and more extended, experiments were wholly 

 negative. Not once were these investigators again able to transmit 

 the infection of poliomyelitis through Stomoxys. They concluded that 

 it was extremely doubtfxd that the insect was an important factor 

 in the natural transmission of the disease, not only because of their 

 series of negative results, "but also because recent experiments have 

 afforded additional evidence of the direct transmissibility or con- 

 tagiousness of poliomyelitis, and because epidemiological studies 

 appear to us to indicate that the disease is more likely transmitted 

 largely through passive human virus carriers." 



Soon after this, Kling and Levaditi (1913) published their detailed 

 studies on acute anterior poliomyelitis. They considered that the 

 experiments of Flexner and Clark (and Howard and Clark), who fed 

 house-flies on emulsion of infected spinal cord, were under conditions 

 so different from what could occur in nature that one cotold not 

 draw precise conclusions from them regarding the epidemiology of 

 the disease. They cited the experiments of Josefson (1912), as 

 being under more reasonable conditions. He sought to determine 

 whether the inoctilation of monkeys with flies caught in the wards of 

 the Hospital for Contagious Diseases at Stockholm, where they had 

 been in contact with cases of poliomyelitis, would produce the 

 disease. The results were completely negative. 



Kling and Lavaditi made four attempts of this kind. The flies 

 were collected in places where poliomyelitics had dwelt, three, four 

 and twenty-four after the beginning of the disease in the family and 

 one, three, and fifteen days after the patient had left the house. 

 These insects were for the greater part living and had certainly been 

 in contact with the infected person. In addition, flies were used 

 which had been caught in the wards of the Hospital for Contagious 

 Diseases at Soderkoping, when numbers of poliomyelitics were con- 

 fined there. Finally, to make the conditions as favorable as possible, 

 the emulsions prepared from these flies were injected without previous 

 filtering, since filtration often causes a weakening of the virus. In 



