244 
Arthropod Transmission of Disease 
The results 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 
results 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 doubtful 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 could not 
draw precise conclusions from them regarding the epidemiology of 
the disease. They cited the experiments of Josef son (1912), as 
being under more reasonable conditions. He sought to determine 
whether the inoculation 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 
