INSECTS AND HUMAN DISEASE 127 



in the insects, thus proving that the latter may serve as 

 disseminators of the parasite. Providing that the eggs 

 attain the proper stage of development, the fly, acting 

 simply as a carrier, might convey the parasite to man by 

 falling into or depositing its excreta on his food." 



Various non-pathogenic, and therefore relatively un- 

 important, bacilli are carried from place to place by flies ; 

 one species in particular, known as Bacillus prodigiosus, is 

 frequently found on food. "Although the organism is 

 quite harmless, it has arrested attention because it produces 

 blood-red colonies upon the substances on which it grows. 

 The miracle of ' the bleeding host ' in the middle ages has 

 been attributed by modern writers to the development of 

 prodigiosus colonies upon the wafers in damp churches. 

 Because of the characteristic pigment which it produces, 

 Bacillus prodigiosus has been a favourite organism in 

 experimental work. Thus, as early as 1875, Otto Helm 

 experimented with Monas prodigiosa, and stated that the 

 slimy masses containing the bacillus are easily conveyed by 

 flies from one food substance to another." The story might 

 be continued ad nauseam ; we have said enough, however, 

 to show beyond doubt that, as a disseminator of disease, a 

 carrier of unpleasant parasitic worms and of bacilli, which, 

 though non-pathogenic, ruin man's food, the ubiquitous 

 house fly is without a compeer. 



A prevalent disease of children in Scandinavia, Germany, 

 and America, known as infantile paralysis or acute epidemic 

 poliomyelitis, was first recognised in 1840 by Heine, a 

 German surgeon. Since that time the disease has made 

 considerable headway in Europe and America, and has also 

 spread to Australia, the West Indies, and other parts of 

 the world. For several years there has been a growing 

 suspicion amongst those familiar with the disease that it 

 is insect-borne. Sporadic cases occur in such a way as to 

 render it unlikely that they have been contracted by 

 personal contact. The disease almost disappears in winter 



