236 MICRO-ORGANISMS AND DISEASE. [CHAP. 



products has accumulated, the organisms become arrested in 

 their growth, and finally may be altogether killed. Thus the 

 substances belonging to the aromatic series, indol, skatol, 

 phenol, and others, which are produced in the course of 

 putrefaction of proteids, have a most detrimental influence 

 on the life of many micro-organisms, as has been shown by 

 Wernich and others (see Antiseptics). 



It is not well known whether in all or in some of these 

 instances the organisms produce the chemical effects by 

 creating a special zymogen or ferment, and by this create the 

 chemical disturbance, or whether they merely dissociate the 

 compounds by abstracting for their own use certain mole- 

 cules ; but this much is known, that in consequence of this 

 chemical disturbance definite chemical substances are pro- 

 duced. It is quite possible that the pathogenic, like the 

 zymogenic, organisms have this special character, that if the 

 soil (animal body) contains a certain chemical substance, they 

 are capable of growing and thus capable of producing a 

 definite zymogen or ferment. 



In many cases of putrefactive and zymogenic organisms 

 a definite soil may be capable of furnishing suitable material 

 for various organisms at the same time ; as a matter of fact 

 this is what one constantly meets with in ordinary putrefac- 

 tion of vegetable and animal matter, which teem with various 

 species of micro-organisms. But as a rule it will be observed 

 that one species is more apt to find a suitable soil in this 

 substance than others ; and then it will be found that this one 

 organism, above all others, grows more numerously ; and when 

 it has done growing, that is, when it has exhausted its own 

 peculiar pabulum, another organism, not dependent on this, 

 but on some other substance present, makes a good start 

 and multiplies accordingly. Thus one finds constantly, that 

 a fluid, supposing it contains a variety of proteids, carbo- 



