48 



ESSENTIALS OF CHEMICAL PHYSIOLOGY 



of changes, known as putrefaction which are accompanied by the 

 formation of malodorous gases and which are produced by the growth 

 of various forms of bacteria, also come into the same category. 



That the change or fermentation is produced by these organisms 

 is shown by the fact that it occurs only w^hen the organisms are 

 present, and stops when they are removed or killed by a high tem- 



Pic. 16. — Typical forms of Scliizomycetes Cafter Zopf ) ; n, micrococcus: h, iiiacrococcus ; <r, bac- 

 terium : rf, bacillus ; e, clilostridiiim ; /", lloiias Okenii ; </, loptothrix ; h, i, vibrio ; k, sinrilUim ; 

 /, spirulina ; m, spiroinoiias ; n, s])irocU:iite ; o, cladothrix. 



perature or by certain substances (carbolic acid, mercuric chloride, 

 &c.) called antiseptics. The organisms probably produce fermenta- 

 tive effects by shedding out soluble ferments or en^^ymes. 



The ' germ theory ' of disease explains the infectious diseases by 

 considering that the change in the system is of the nature of fermen- 

 tation, and, like the others we have mentioned, produced by microbes ; 

 the transference of the bacteria or their spores from one person to 

 another constitutes infection. The poisons produced by the growing 

 bacteria appear to be either alkaloidal (ptomaines) or proteid in 



