August, "12] BRLES AND SHEPPARD: INFANTILE PARALYSIS 



307 



4. The characteristic rural nature of the disease, which is apparently 

 always less prevalent in large cities where the proportion of insects to 

 the human population is less than it is in more sparsely settled or in 

 rural districts. 



5. The fact that in towns in Massachusetts, where the disease has 

 been most prevalent, the proportion of animals to the population is 

 greater than in cities, where the disease is less prevalent. This in 

 itself implies a larger number of biting and parasitic insects which 

 affect man as well as the animals. 



Total number of animals assessed in twenty-five 

 cities and towns where the disease was least preva- 

 lent, i. €., in the larger cities and towns. 



Total number of animals assessed in the twenty-five 

 cities and towns where the disease was most preva- 

 lent, i. e., in the smaller cities and towns. 



Total population 943,614 



Total number of cows n,160 



1 cow to 84.5 inhabitants 

 Total number of horses 29,519 



1 horse to 32 inhabitants 

 Tfftal number of swine 3,288 



1 swine to 2S7 inhabitants 

 Total number of fowls 41.887 



1 fowl to 22.5 inhabitants 

 Total number of dogs 23,854 



1 dog to 39.5 inhabitants 



Total population 142,639 



Total number of cows 12,801 



1 cow to 11 inhabitants 

 Total number of horses 10,352 



1 horse to 14 inhabitants 

 Total number of swine 2,374 



1 swine to 60.5 inhabitants 

 Total number of fowls 79.797 



1 fowl to 1 .75 inhabitants 

 Total number of dogs 5,865 



1 dog to 24.3 inhabitants 



These facts seem to point very strongly to an insect-borne disease. 



Other facts which bear out the supposition that the disease might 

 be insect-borne are added, although they do not appear to be less 

 easily explained in other ways, at least when considered separately. 

 These are: 



1. The greater incidence of the disease among children, which are 

 more apt to be bitten by insects than are adults under ordinary con- 

 ditions. 



2. The apparent biennial recurrence in the incidence of the disease 

 in localities where it has been epidemic. This, as will be seen from 

 considerations presented later in the report, would seem to imply a 

 secondary connection with ticks, if there be any foundation in the 

 belief that there is a relationship between animal and human paralyses. 



In addition to these data, there is a negative evidence afforded by 

 the failure of investigators satisfactorily to account for the spread of 

 anterior poliomyelitis through the other channels of infection that are 

 concerned in the dissemination of most infectious diseases in temperate 

 regions. 



It is apparent, therefore, that an investigation of the insect fauna 

 associated with cases of the disease seemed advisable, with a view 



