THE METHODS OF BACTERIAL ACTION 23 



though not concerned in ordinary putrefactive processes, have 

 a similar digestive rapacity. When carbohydrates are being 

 split up, then various alcohols, ethers, and acids are produced. 

 l)uring bacterial growth there is not infrequently the abundant 

 production of such gases as sulphuretted hydrogen, carbon 

 dioxide, methane, etc.. For an exact knowledge of the de- 

 structive capacities of any particular bacterium there must be 

 an accurate chemical examination of its effects when it has 

 been grown in artificial media the nature of which is known. 

 The precise substances it is capable of forming can thus be 

 found out. Many substances, however, are produced by 

 bacteria, of the exact nature of which we are still ignorant, 

 for example, the toxic bodies which play such an important 

 part in the action of many pathogenic species. 



Many of the actions of bacteria depend on the production by 

 them si ferments of a very varied nature and complicated action. 

 Thus the digestive action on albumins probably depends on the 

 production of a peptic ferment analogous to that produced in the 

 animal stomach. Ferments which invert sugar, which .split 

 up sugars into alcohols or acids, which coagulate casein, which 

 split up mva into ammonium carbonate, also occur. 



Such ferments may be diffused into the surrounding fluid, or 

 be retained in the cells where they are formed. Sometimes the 

 breaking down of the organic matter appears to take place 

 within, or in the immediate proximity of, the bacteria, some- 

 times wherever the soluble ferments reach the organic substances. 

 And in certain cases the ferments diffusing out into the surround- 

 ing medium probably break down the constituents of the latter 

 t-> some extent, and prepare them for a further, probably 

 intracellular, disintegration. Thus, in certain putrefactions of 

 fibrin, if the process be allowed to go on naturally, the fibrin 

 dissolves and ultimately great gaseous evolution of carbon 

 di>xidf and ammonia takes place, but if the bacteria, shortly 

 after the process has begun, are killed or paralysed by chloro- 

 form, then only a peptonisation of the fibrin occurs, without 

 the further splitting up and gaseous production. That a 

 purely intracellular digestion may take place is illustrated by 

 what has been shown to occur in the case of the micrccoccus 

 urea-, which from urea forms ammonium carbonate by adding 

 water to the urea molecule. Here, if after the action has 

 commenced the bacteria are filtered off, no further production 

 of ammonium carbonate takes place, which shows that no 

 ferment has been dissolved out into the urine. If now the 

 bodies of the bacteria be extracted with absolute alcohol or ether, 



