xix.] PATHOGENIC ORGANISMS. 179 



anthracis as the tissues and juices obtained from a herbivorous 

 animal ; artificial cultures of the former and of the latter 

 behave in exactly the same manner, both as regards copiousness 

 of growth and virulence of the bacilli. Again, artificial cultures 

 of the bacillus of swine-plague made in juice of the tissues of 

 the guinea-pig or fowl are exactly the same as those made of 

 the juice of the tissues of a rabbit or pig. The tissues, there- 

 fore, per se cannot be said to possess any inimical action on the 

 organisms. The living condition per se can also not have this 

 power, since we see that the power to overcome the influence 

 of the living tissue is precisely the great distinguishing 

 character of pathogenic organisms. There remains, therefore, 

 only one thing, that is that there is something or other present 

 in a particular tissue to which this latter owes its immunity, 

 and this something must of necessity be connected with the 

 tissue while alive, as we said before. Now, the life of the 

 tissue in the pig cannot be different from that of the mouse, if 

 by life is understood the function of the tissue, the connexion 

 with the vascular and nervous system, and all the rest of it. 

 The subcutaneous connective tissue has no different function, 

 no different relation to the vascular and nervous system in the 

 pig from what it has in the mouse, and nevertheless we find 

 that it behaves so differently in the two cases towards the 

 bacillus anthracis. This something then, which inhibits the 

 growth and multiplication of the bacillus anthracis in the 

 tissue of the pig but not in the mouse, must be something 

 which, although dependent on the life of the tissue, is not 

 identical with any of the characters constituting the life of the 

 tissue, but must be some product of that life. To assume then, 

 as is done by some observers, that the living state of the cells 

 per se is the inhibitory power does not cover the facts, as we 

 have just shown. The most feasible theory seems to me to be 

 this, that this inhibitory power is due to the presence of a 

 chemical substance produced by the living tissues. It does not 

 require any great effort to conceive, and it does not seem at all 

 improbable, that the blood and tissues of the pig contain 

 certain chemical substances which are not present in the 

 mouse, substances which like so many others chemistry is not 

 yet capable of demonstrating. But that there exist vast and 

 gross differences in the chemical constitution of the blood and 

 tissues of different species of animals there can be no 

 reasonable doubt ; it is a fact with which physiological 

 chemistry is quite familiar. 



We arrive then, after all this, at the conclusion that owing 

 to the presence in the blood and tissues of particular chemical 



N 2 



