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not grow nor reproduce. But at any time previous to 

 this final extinction of vitality, the bacilli still exhibit life, 

 though their ability to invade a living animal, i.e., their 

 malignancy, is diminished. There occurs, indeed, a grad- 

 ual diminuendo of malignancy, their morbid effect upon 

 an animal decreasing with the prolongation of their ex- 

 posure to these conditions, high temperature and exclu- 

 sion of oxygen, until finally both life and malignancy are 

 extinguished. Pasteur found that after eight days the 

 bacilli had lost their fatal power to destroy rabbits, guinea- 

 pigs, and sheep, though these animals are peculiarly sus- 

 ceptible to this virus. He claims that he has thus miti- 

 gated the virulence of these bacteria, has induced a 

 modification of function. 



As to the accuracy of Pasteur's observation in this case 

 there can be no doubt ; the vaccination of thousands of 

 animals has already proven that the mortality induced by 

 such anthrax cultures is much less than that following the 

 usual inoculations with fresh virus. But his explanation, 

 that the decrease of malignancy is due to modification of 

 physiological function, is a by no means necessary con- 

 clusion, since precisely the same results can be and have 

 been secured, under circumstances which preclude the 

 possibility of a transmissible physiological modification. 



First among these methods is simple dilution. It has 

 been long since and often demonstrated that the effect 

 induced by the incorporation of these virulent organisms 

 into an animal depends, catcris paribus, upon the number 

 introduced. Chauveau found that sheep which had sur- 

 vived injections of fifty to six hundred anthrax bacilli 

 died after subsequent injections of one thousand bacilli 

 each. Oemler had previously made analogous observa- 

 tions upon horses ; Loffler upon rats ; it is indeed an ac- 

 cepted principle that the effect of inoculation increases 

 with the number of injected bacilli. The somewhat 

 general impression that quantity exerts no influence upon 

 the result, except as to time, maybe true when the effect 

 is manifested upon an inert, unorganized mass, but not 

 in the case of a living animal. 



