274 Illinois State Laboratory of Natural History. 



than if I had wished to discriminate and describe the various 

 forms appearing. I depended upon frequent repetition of the 

 experiments and uniformity of results, rather than upon the 

 more critically exact cultures and continuous observation of 

 current methods with gelatine films and masses. 



Culture Experiments. — Concerning our first cultures, the 

 fact should be remembered that one could rarely expect to find 

 a perfectly pure culture in the body of a diseased insect, 

 exposed as it is by way of the food ingested to invasion by 

 bacteria in great variety. I consequently did not find it 

 remarkable that several of our unquestionably sucessful infec- 

 tions were not really pure cultures, other bacteria developing 

 than those most abundant in the original fluids. For example, 

 in the very first culture made, — one in beef broth begun Sep- 

 tember 16, when the infection process was very carefully man- 

 aged without the slightest accident, and when the check tube 

 remained clear indefinitely, — the culture became turbid the fol- 

 lowing day, and by October 3, was nearly as yellow as cream, 

 with a thick yellowish felt on top and an abundant precipitate. 

 The greater part of the product of this culture consisted of 

 micrococci like the larger of those of the cabbage worm, the 

 spherules, in singles and doubles, averaging 1 ^w in diameter; but 

 the surface film consisted largely of a Saccharomyces embed- 

 ded in the Microccocus. Individuals of Bacterium also oc- 

 curred in the slides. The check tube, as already mentioned, 

 was quite clear to the end. 



The second culture was still less conclusive and satisfac- 

 tory. A cabbage worm which, on the afternoon of the 17th 

 September, was noticeably paler than its companions, was iso- 

 lated and watched. At 9 p. m. it seemed a little stupid, but 

 otherwise unchanged. At 9 a. m. of the 18th, however, it was 

 dead, blackened, and very soft, the contents evidently little 

 better than fluid. These fluids contained two micrococci, — one 

 a larger spherical or slightly quadrate form, 1 ;«. in diameter, and 

 the other a minute spherule .5 fi to .75 n. 



A small flask of rather weak beef infusion was infected 

 from these fluids in the usual manner, and the next day, the 

 19th, it was already (^ecidedly milky. Examined, it was found 

 to contain Bacterium and the larger Micrococcus above men- 



