126 INSECTS AND MAN 



those found in the conjunct! val secretion." Other authors 

 are agreed that the evidence regarding the spread of 

 Egyptian ophthalmia by flies is conclusive. 



"The first to investigate the house fly in relation to 

 the possible dissemination of the tubercle bacillus were 

 Spillman and Haushalter (1887). These authors found 

 tubercle bacilli in the intestinal contents and dejections of 

 flies which had fed on tubercular sputum. Hofmann 

 (1888) carried out observations under natural conditions 

 by examining flies captured in the room of a phthisical 

 patient. He found tubercle bacilli in four out of six flies 

 examined, and also in the excreta of flies scraped from the 

 walls, door, and furniture of the room. Celli (1888) has 

 reported experiments by Alessi in which the latter fed 

 flies upon tubercular sputum, and subsequently inoculated 

 the flies' dejections into rabbits, thus causing the latter 

 to become tuberculous." Later experiments by Hayward 

 (1904) and Buchanan (1907) showed that, without a doubt, 

 flies are capable of spreading tuberculosis. The cup is not 

 yet full, for the ubiquitous house fly has also been accused, 

 and not without reason, though the proof is not yet forth- 

 coming, of spreading diphtheria, dysentery, yaws, plague, 

 tropical sore, small-pox, and swine fever. 



We have stated in another place that, normally, the food 

 of adult house flies is taken up in liquid form. In this 

 connection some interesting experiments by Grassi (1883) 

 and Stiles (1889) are of importance. Grassi showed, when 

 flies sucked up water in which the eggs of parasitic worms 

 were floating, that they were absorbed with the liquid and 

 passed away unaltered in the insects' dejections. Stiles 

 placed house-fly maggots with the female of another 

 parasitic worm, which they devoured, together with the 

 contained eggs. Both the maggots and the adult flies were 

 found to contain the eggs of the parasite. " The experi- 

 ment being made in very hot weather, the eggs developed 

 rapidly, and were found in different stages of development 



