202 TEXT-BOOK OF BACTERIOLOGY. 



normal bacilli. The cause of this striking- phenomenon is to be 

 sought in the action of deleterious influences, which rob the pro- 

 toplasm of a power which it had previously possessed. Thus, 

 according to Roux, one can with certainty obtain permanently 

 sporeless bacilli by breeding them for some time in a food fluid 

 containing just so much carbolic acid about 1 : 1,000 as not to 

 -completely stop the growth of the bacteria. 



The anthrax spores are of great importance to us for many 

 reasons. The bacilli themselves are comparatively tender organ- 

 isms, which at high temperatures (above 60 C.) quickly perish, and 

 which are also so little able to bear desiccation that even in tolerably 

 large portions of tissue they can at most retain their vitality for a 

 few weeks. The spores, on the other hand, possess all the qualities 

 of a genuine permanent form and are able to preserve the species 

 against all hostile influences. It is with difficulty that we can de- 

 stroy them by chemical or physical means, and of the forces which 

 nature can bring to bear against them, we know of none that could 

 harm them with the one exception of sunlight. 



In consequence of its high power of resistance, the anthrax spore 

 has become the most favored of all test-objects for experiments in 

 disinfection. We require of a means for disinfection that it shall 

 with certainty destroy the source of infection which offers the 

 greatest resistance to our destructive efforts, and that source is 

 certainly the anthrax spore. We test a disinfecting process by 

 exposing to its action silk threads on which spores have been dried. 

 The process has not passed the test till the threads can be after- 

 ward placed on a fresh culture medium without causing a develop- 

 ment of bacteria. 



In all such tests we must take a phenomenon into account 

 which has been treated of at length by E. von Esmarch, namely, 

 that there exists a striking difference in the power of resistance of 

 spores obtained from different sources. The considerable differences 

 to be observed in the behavior of different bacteria of the same 

 species as regards their external influences have already been noticed, 

 and this is a particularly striking proof of the correctness of that 

 assertion. It is, therefore, well to always examine spore -threads 

 and ascertain the degree of their power of resistance before em- 

 ploying them as tests. 



In the preparation of spore-threads, it is best to take the mate- 

 rial from the surface of good agar cultures. In the- incubator they 

 usually form abundant spores in twenty-four to thirty-six hours. 

 When convinced of their existence by means of a hanging drop, 

 then scrape the coating from the culture medium with a sterilized 



