Il8 HUGH GLASGOW. 



With this as an encouragement, an excessive amount of time 

 and effort was wasted in an attempt so to modify culture condi- 

 tions that the normal caecal organism of this insect could be 

 induced to grow on artificial media. Since, in reaction, the caeca 

 appear faintly alkaline, the different media used were usually 

 made neutral or slightly alkaline; and as the normal food of the 

 insect is cabbage, this was largely used in the different media 

 tested; but as all the results were uniformly negative, no minute 

 discussion will be given here of the different modifications that 

 were tried. Anaerobic cultures were also made with negative 

 results, although at the time, this test seemed almost superfluous 

 in view of the abundant tracheation of the caeca. 



After the failure of these direct culture experiments, it was 

 reasoned that upon the death of the insect the bacteria probably 

 became gradually adapted to a saprophytic mode of life, and that 

 by taking advantage of this they might still be forced to grow on 

 artificial media. 



In testing this hypothesis, several series of from forty to fifty 

 insects each were used. The insects were killed either with 

 chloroform or by grasping the head for an instant with a pair 

 of very hot forceps, the last method being the one most generally 

 used and proving a very convenient way of killing the insect 

 without breaking the body wall. The dead insects were then 

 thoroughly sterilized by washing in a mercuric chloride solution 

 after the removal of the wings, and after drying they were placed 

 in small, tightly stoppered, sterile vials, to prevent drying of 

 the internal structures, and kept for three or four days in a cold 

 box at about 20 C. At the end of this time the alimentary 

 canal was usually intact and showed no invasion by foreign 

 bacteria, while the caecal bacteria themselves showed no percep- 

 tible changes either in numbers or in the invasion of other regions. 

 Bouillon tubes inoculated from the caeca of these dead bugs 

 usually remained sterile, but growth appeared in two or three per 

 cent, of the tubes, and it was thought at first that this growth 

 might represent strains of the caecal organism which had been 

 modified by their stay in the dead bugs so as to develop on artifi- 

 cial media. When these cultures were examined under the micro- 

 scope, however, they showed, not the long, irregularly bent 



