276 Illinois State Laboratory of Natural History. 



were micrococci at all, notwithstanding their uniform shape, 

 size, and character, and the fact that they were repeatedly dis- 

 tinctly stained ; or (2), taking for granted their bacterial 

 nature, we may suppose them insusceptible of culture under 

 the conditions supplied; or, finally (3), we may assume that 

 the conditions of tube culture in beef broth were so different 

 from those occurring within the blood of the insect as to in- 

 crease the size or even modify the form of the Micrococcus in 

 question. In favor of the latter hypothesis we have the fact 

 of the generally larger size and often slightly oval form of the 

 micrococci found in the intestinal fluids, as compared with 

 those in the blood of the same specimen. 



These considerations apply, however, only to the minute 

 blood form, and not at all to the intestinal Micrococcus. This I 

 have cultivated repeatedly with indubitable success in this 

 insect, and, still more frequently, forms indistinguishable from 

 it occurring in other species. I venture to add that the 

 frequency with which certain bacteria, different from the 

 infection material, appeared in the test tubes when these were 

 infected from the cabbage worm, suggested repeatedly the 

 hypothesis of an alternation of certain forms which were in this 

 way frequently connected, — a point on which I shall have more 

 to say when describing the Datana bacteria. Especially was 

 this true of the larger Micrococcus and of the short, broad 

 Bacillus (?) with pale center and rounded ends (here called, for 

 convenience. Bacillus intrapallens) . The latter, I shall presently 

 show, behaved precisely like a pathogenic form, — giving no 

 odor of putrefaction in fluids swarming with it, killing insect 

 larvae whose food was treated with it, and certainly multiplying 

 for some days within their living bodies. 



The late period at which successful cultures of the cabbage 

 worm Micrococcus were made precluded attempts at artificial 

 infection by their means, and with respect to this particular 

 insect this part of the proof is consequently wholly wanting. 



When the evidence is given respecting the reproduction of 

 what wa,s clearly the same disease in other insects, I think that 

 no reasonable doubt will remain that Jiacherie of the cabbage 

 worm may be conveyed through artificial cultures of its Micro- 

 coccus. 



