ANNIVERSARY ADDRESS. 29 



Now, what is there in the nature of things to account for this 

 process of putrefaction ? The coke, like a sponge, is full of inter- 

 stices and holds a large volume of atmospheric air, which is destined 

 to play an important part in the process; carbon, as is well known, 

 has the property of holding large volumes of gases ; common 

 charcoal can take up ninety times its own volume of ammonia gas. 

 A fermentation is inaugurated in the sewage under these condi- 

 tions, the sewage itself containing the micro-organism necessary 

 for its own decomposition. Proteids break up, their nitrogen 

 being changed into ammonia ; urea is transformed into ammonia 

 carbonate ; sulphur is changed to hydrogen sulphide. Hydrogen 

 is recombined to form methane ; carbon takes oxygen to appear 

 again as the dioxide ; while some of the nitrogen suffers differing 

 degrees of oxidation, appearing as the lower oxides and sometimes 

 is even reduced to free nitrogen. 



This change has been called the biological treatment of sewage, 

 or the biolysis of sewage, (Scott-Moncrieff) ; or as I propose, I 

 think, more correctly — the zymolysis of sewage. The fermentation- 

 change known as putrefaction or decomposition, and tersely des- 

 cribed by Duclaux in the following words: — "Whenever and 

 wherever there is a decomposition of organic matter, whether it 

 be the case of a herb or an oak, of a worm or a whale, the work 

 is exclusively done by infinitely small organisms. They are the 

 important, almost the only, agents of universal hygiene ; they 

 clear away more quickly than the dogs of Constantinople, or the 

 wild beasts of the desert, the remains of all that has had life; they 

 protect the living against the dead. They do more ; if there are 

 still living beings, if, since the hundreds of centuries the world 

 has been inhabited, life continues, it is to them we owe it." 



The appearance and disappearance of nitrogen is remarkable. 

 During many years experience in the examination and analysis of 

 sewage and sewage effluents, I have been unable to find nitrites, 

 and very often have failed to find any nitrous or nitric nitrogen 

 at all. During some recent researches as to the true composition 

 of sewage, it was decided to take samples of sewage at all hours 



