298 FRAGMENTS OF SCIENCE 



at tlie end of three or four hours thej attained from ten 

 to twenty times their original length. At the end of a 

 few additional hours they had formed filaments in many 

 cases a hundred times the length of the original rods. 

 The same filament, in fact, was frequently observed to 

 stretch through several fields of the microscope. Some- 

 times 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 con- 

 fusion. 



Had the observation ended here an interesting scien- 

 tific fact would have been added to our previous store, 

 but the addition would have been of little practical value. 

 Koch, however, continued to watch the filaments, and after 

 a time noticed little dots appearing within them. These 

 dots became more and more distinct, 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 respects by the celebrated naturalist, Cohn 

 of Breslau, are of the highest importance. They clear up 

 the existing perplexity regarding the latent and visible 

 contagia 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 



