238 MICRO-ORGANISMS AND DISEASE. [CHAP. 



the bacillus anthracis cannot grow in the living tissues of 

 the living pig, dog, or cat, but grows well in those of rodents, 

 ruminants, and man ; the bacillus of swine-plague grows 

 well in the pig, rabbit, and mouse, but not in the guinea-pig 

 or man. 



Septic organisms differ also from pathogenic organisms in 

 this, that the former are capable of growing in fluids contain- 

 ing only simple nitrogenous compounds, e.g. tartrate of am- 

 monia, whereas pathogenic organisms require more complex 

 combinations, proteids, or allied nitrogenous substances. 

 Thus, for instance, in Cohn's and Pasteur's fluids septic 

 micrococcus, bacterium, and bacillus grow well and copiously, 

 but pathogenic organisms absolutely refuse to grow in them ; 

 even bacillus anthracis, which appears the least selective, 

 cannot make a start in it. Some organisms, e.g. tubercle- 

 bacilli, require the most complex nitrogenous compounds ; 

 they refuse to grow, for instance, in broth in which anthrax- 

 bacilli, bacilli of swine-plague, micrococcus diphtheriticus 

 and erysipelatous can grow well. 



All septic and zymogenic organisms properly so-called, 

 and described in former chapters, differ in this essential 

 respect from pathogenic organisms, that the former two 

 absolutely refuse to grow in the living tissues of a living 

 animal. 



As was stated in former chapters, it is not at all uncommon 

 to find masses of micrococci in tissues which during the life 

 of the subject have become dead or necrotic, or so severely 

 changed by inflammation or otherwise that they may be con- 

 sidered as practically dead. In the diseased, necrotic 

 intestine, the liver, the spleen, in abscesses, in the subcu- 

 taneous, submucous, or parenchymatous tissues, masses of 

 micrococci have been noticed which in no way bear any 

 intimate relation to disease, merely finding in the dead or 



