INFECTION FJtOM FLIES JUIED IN INFECTED MATEKIAL 227 



III ;i series of experiments with Bacillus pijOcyaneuH Bacot 

 (J 911) appears to prove conclusively that this bacillus if ingested 

 during the larval life of M. doinestica is able to retain its existence 

 during the complex changes accompanying metamorphosis and to 

 continue its existence in the gut of the adult Hy after emergence 

 from the puparium. He points out that the Hies in Faichnie's 

 experiments may have re-infected themselves by feeding on the 

 contaminated material. To avoid the possibility of this in his 

 experiments the pupae were sterilised and placed in clean sand in 

 clean tubes. Commenting on Bacot's experiments, Ledingham 

 states in a footnote that he has successfully isolated B. typhosius 

 from pupae of M. doinestica, the larvae having fed on the organism. 

 All chances of external infection from the exterior of the puparium 

 were removed by the careful method he devised of examining the 

 bacterial content of the pupal interior. The puparium was held 

 lightly between the left thumb and forefinger so that its blunt 

 extremity was free. The extremity was seared by means of 

 a small searing iron, and at the same time flattened. It was then 

 pierced by a fine capillary pipette controlled by a rubber teat. 

 The pupal contents are stirred up by the extremity of the pipette 

 and finally drawn up into the tube whence they are squirted on to 

 culture plates. 



In a later paper Ledingham (1011) has carried his investi- 

 gations still further, and shows that although B. typhosus was 

 supplied in considerable quantities to the larvae of M. domestica, 

 all attempts to demonstrate the bacillus in the pupae or resulting 

 adult tiies were unsuccessful until recourse was had to the disinfec- 

 tion of the ova. After this preliminary disinfection both larvae 

 and pupae gave pure growths of B. typhosus. The author's chief 

 conclusion appears to be that the typhoid bacillus can lead only 

 a very precarious existence in the interior of the larvae or pupae 

 which possess apparently a well-defined bacterial flora of their 

 own, as Nicoll (1911) has recently shown. In the experiments it 

 was not really possible to determine whether the B. typhosus, though 

 recoverable from the pupae, was in fact actively multiplying in the 

 pupal interior or gradually dying out. There was some indication 

 that the latter was the case, as the typhoid colonies recovei'ed 

 from the pupa in the one successful instance were extremely few 



15—2 



