president’s address. 
17 
soil knoM'u to be easily nitriliable, such as the soil of a “ fairy-ring;” 
that such nitrification coukl also he totally arrested by ■well-known 
antiseptics such as chloroform, bisulphide of carbon, carbolic acid, 
etc. ; and he therefore concludes that the nitrification observed in 
soils and waters is due to the growth of a Mycoderni, and that the 
lirocess is analogous to acetic fermentation in which alcohol is 
oxidized by the growth of the Mycoderma aceii. 1 need hardly say 
that these deductions arc still disputeil by some scientific men, and 
experiments have been made to prove that nitrification may take 
place by simple oxidation due to the oxygen of the air ; but these 
experiments unfortunately have not lieeii conducted with the care 
necessary to exclude atmospheric contaminations, which at once 
vitiate the evidence. The marvellously exact methods of Pa.steur 
in removing all possible sources of uncertainty in dealing with such 
experimental evidence have not been followed, and hence no 
reliance can be placed upon the results. 
In summing up the evidence as to the theory that nitrification is 
due to a living organism, I cannot ilo better than (;uote the words 
of ^Ir. Warington in his last report on the suliject to the Chemical 
Society : — 
“ Tlic evidence in fiivour of this theory of nitrification appears 
now to be very complete. iXitrificatiou in soils and ■waters is found 
to bo strictly limited to the range of temperature to which the 
vital activity of low organisms is confined. Nitrification is also 
dependent on the presence of plant-food suitable to organisms of 
low character. Further proof is afforded by the fact that antiseptics 
are fatal to nitrification. The action of heat is equally confirmatory. 
]>y raising sewage or soil to the tempei-ature of boiling water, its 
nitrifying power is entirely destroyed. Finally, nitrification can be 
started in boiled sewage, or in other sterilised liquids of suitable 
composition, by the addition of a few particles of surface soil, or a 
few drops of a solution which has lately nitrified ; while if no such 
addition is made, these liipiids may be freely exposed to filtered air 
without nitrification taking place. 
“ It is difficult to conceive how the evidence in favour of the 
VOL. iv. 
c 
