130 TEXT-BOOK OF BACTERIOLOGY. 



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of the phenomenon of diminished virulence. The question would 

 then merely have to be put in another form : Why is the healthy 

 protoplasm able to grow and thrive in the bodies of susceptible 

 animals, and the degenerated protoplasm not ? 



We know a few facts, however, which may, perhaps, give a 

 glimpse into these matters. We have characterized the patho- 

 genic bacteria in general as those which produce substances poi- 

 sonous to our own bodies or to those of animals. Virulent and at- 

 tenuated anthrax bacilli stand in the same relation to each other 

 as pathogenic and the non-pathogenic species. Do not the excre- 

 tions here also play the chief role ? 



The investigations of Behring have yielded at least the begin- 

 ning of a confirmation of Ms supposition. Behring found that viru- 

 lent bacilli anthracis formed considerably more acid than attenu- 

 ated ones, but that the latter possessed a far more decided power 

 of reduction. These certainly appear but slight differences, but it 

 is probable that these differences, which are perceptible on a rough 

 examination, are but the outward expressions of finer, deeper phe- 

 nomena; that the greater or less quantity of alkali produced only 

 stands as the indicator of more complicated processes which are, 

 as yet, beyond the limits of our perception. Not until our knowl- 

 edge of the products excreted by the bacteria in general has be- 

 come more complete when, for instance, we are able to give a 

 definite answer to the question, What chemical substances are pro- 

 duced by the vital functions of the virulent anthrax bacilli ? not till 

 then can we expect final results. * 



The observations already made enable us, at any rate, to form 

 an idea of these matters which may, perhaps, not be in accordance 

 with reality, but which at least points to a possible explanation of 

 the existing difficulties. 



Let us say the relation between the bacteria on the one side 

 and an animal organism on the other is characterized in the main 

 by the latter opposing certain hindrances to the penetration and 

 multiplication of the parasites which the latter have to overcome. 

 As will presently be seen, this is by no means a mere supposition, 

 but a fact grounded on reliable observations. It is only as to the 

 nature of these hindrances that we are in the dark. 



But let us suppose them to be of a purely chemical nature. 

 White rats are, as a rule, insusceptible to anthrax, or in other 

 words, the anthrax bacilli are not able to thrive in the bodies of 

 these animals. The reason is, according to the investigations of 

 Behring, that the blood and the tissue-juices of the rats possess an 

 extremely high degree of alkalescence, which renders it impossible 



