XVIIL] NON-PATHOGENIC ORGANISMS. 173 



has been split up into alcohol and carbonic acid, the latter 

 escaping as gas, then the material is ready for the organisms 

 capable of converting the alcohol into acetic acid. The two 

 kinds of organisms may be, however, growing at the same time, 

 the saccharomyces leading. 



Septic or putrefactive organisms then, like zymogenic and 

 pathogenic organisms, are cceteris paribus, dependent for their 

 growth on the presence of the suitable nourishing material. 

 And, as we have seen, they differ materially from one another 

 in this respect ; while putrefactive organisms find in almost 

 all animal and vegetable fluids the necessary substances for 

 nutrition, the zymogenic and pathogenic organisms are much 

 more limited in these respects. Where there is no alcohol 

 present the organisms producing the acetic acid fermentation 

 cannot grow ; where there is no sugar or a similar substance 

 present the saccharomyces cannot grow, and so also a particular 

 pathogenic organism 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 patho- 

 genic 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, diifer 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 subcutaneous, sub- 



