282 FRAGMENTS OF SCIENCE. 



through several fields of the microscope. Sometimes 

 they lay in straight lines parallel to each other, in other 

 cases they were bent, twisted, and coiled into the most 

 graceful figures; while sometimes they formed knots of 

 such bewildering complexity that it was impossible for 

 the eye to trace the individual filaments through the 

 confusion. 



Had the observation ended here an interesting sci- 

 entific fact would have been added to our previous 

 store, but the addition would have been of little prac- 

 tical value. Koch, however, continued to watch the 

 filaments, and after a time noticed little dots appearing 

 within them. These dots became more and more dis- 

 tinct, until finally the whole length of the organism 

 was studded with minute ovoid bodies, which lay within 

 the outer integument like peas within their shell. By- 

 and-by the integument fell to pieces, the place of the 

 organisms being taken by a long row of seeds or spores. 

 These observations, which were confirmed in all re- 

 spects by the celebrated naturalist, Cohn of Breslau, 

 are of the highest importance. They clear up the ex- 

 isting complexity regarding the latent and visible con- 

 tagia of splenic fever; for in the most conclusive man- 

 ner, Koch proved the spores, as distinguished from the 

 rods, to constitute the contagium of the fever in its 

 most deadly and persistent form. 



How did he reach this important result? Mark the 

 answer. There was but one way open to him to test 

 the activity of the contagium, and that was the inocu- 

 lation with it of living animals. He operated upon 

 guinea-pigs and rabbits, but the vast majority of his 

 experiments were made upon mice. Inoculating them 

 with the fresh blood of an animal suffering from splenic 

 fever, they invariably died of the same disease within 

 twenty or thirty hours after inoculation. He then 



