282 FKAGMENTS OF SCIENCE. 



bewildering complexity that it was impossible for the 

 eye to trace the individual filaments through the con- 

 fusion. 



Had the observation ended here an interesting 

 scientific 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 exist- 

 ing perplexity regarding the latent and visible contagia 

 of splenic fever; for in the most conclusive manner, 

 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 

 sought to determine how the contagium maintained its 

 vitality. Drying the infectious blood containing the 

 rod-like organisms, in which, however, the spores were 

 not developed, he found the contagium to be that which 



