GASTRIC C^ECA OF THE HETEROPTERA. IIJ 



solution or bouillon as just described, crush it, and from this 

 make plate cultures in the usual manner, it being fully expected 

 that a number of doubtful forms of bacteria would be isolated as 

 contamination from the ordinary transient intestinal flora as- 

 sumed to be present in the insects. It was a decided surprise, 

 however, when not only the typical caecal bacteria failed to 

 appear in these plates, but no contaminating forms even de- 

 veloped. This was repeated with large series of the insects but 

 the results were always the same, the cultures remaining sterile 

 with a discouraging regularity. It was thought at first that 

 perhaps the liberal amount of alcohol and bichloride solution 

 used in disinfecting the outer surface of the insects might possibly 

 have penetrated the tracheal system and that enough had been 

 removed with the trachea adhering to the caeca to prevent all 

 growth in the cultures, although this seemed hardly possible. 

 Tests were made, however, in which only those parts of the insect 

 which were actually to be cut were moistened with the dis- 

 infectant, the spiracles being avoided entirely, and the results 

 were exactly the same, the cultures remaining uniformly sterile. 

 It was later found also that without the use of any disinfecting 

 solution the glands could be removed with no fear whatever of 

 contamination from without, provided the scissors with which 

 the cutting was to be done were used hot enough to sear as the 

 body wall was opened ; the cuts being made as rapidly as possible 

 to avoid the danger of heating the tissues too deeply. 



While the apparent incapacity of the csecal bacteria from this 

 insect to develop on ordinary media was somewhat discouraging, 

 at least one very important fact was brought out by it. Since 

 no growth at all developed from the caeca on ordinary media, 

 it was very clear that, contrary to what had been expected, there 

 would be no complication of contaminating organisms from the 

 intestine which are so common in many other insects, since in 

 Murgantia these forms seemed, for some very definite reason, to 

 be wholly absent; and it followed that, if by any means condi- 

 tions could be made suitable for the development of the caecal 

 bacteria of this insect on artificial media, the difficulty of proving 

 that the organism in culture was really the one sought and not 

 some accidental contaminating form would be wholly avoided. 



