22 GENERAL MORPHOLOGY AND BIOLOGY 



In these circumstances, therefore, the production of albumoses, 

 peptones, etc., similar to those of ordinary digestion, can be 

 recognised in putrefying solutions, though the process of destruc- 

 tion always goes further, and still simpler substances, e.g. indol, 

 and, it may be, crystalline bodies of an alkaloidal nature, are 

 the ultimate results. The process is an exceedingly complicated 

 one when it takes place in nature, and different bacteria are 

 probably concerned in the different stages. Many other bacteria, 

 e.g. some pathogenic forms, though not concerned in ordinary 

 putrefactive processes, have a similar digestive capacity. When 

 carbohydrates are being split up, then various alcohols, ethers, 

 and acids are produced. During 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 destructive 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 of 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 

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

 split up urea 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, sometimes 

 wherever the soluble ferments reach the organic substances. 

 And in certain cases the ferments diffused out into the sur- 

 rounding medium probably break down the constituents of 

 the latter to some extent, and prepare them for a further, 

 probably intracellular, disintegration. Thus in certain putre- 

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

 the fibrin dissolves and ultimately great gaseous evolution 

 of carbon dioxide and ammonia takes place, but if the 

 bacteria, shortly after the process has begun, are killed or 

 paralysed by chloroform, then only a peptonisation of the 

 fibrin occurs, without the further splitting up and gaseous pro- 



