1885.] 
Self -Purification of Waters and Soils. 535 
pass through unchanged, it was gradually washed out with 
water. . In the filtrate the ammonia and the nitrates were 
determined, and it was ascertained that, in 167 days, 60 per 
cent of the nitrogen of strychnine reappears in the filtrate 
as .. n ^ :ra ^ e ’ so that in time a complete self-purification of the 
soil from the poison may be expected. 
^hhe fiist traces of nitrates could be detected in the 
filtiate at the expiry of eighteen days. If the soil had ab- 
sorbed quinine a different ultimate product appeared in the 
filtrate, namely, ammonia. This important difference in 
y?!| tiansformation of the alkaloid depends doubtless on the 
diffeient adtion of the alkaloids employed upon the nitrifying 
organisms in the soil. 
Peat possesses a greater absorptive power for alkaloids 
than gravel, but decomposes them much more slowly. If 
solutions of alkaloids were filtered through charcoal, the 
filtiate contained large quantities of carbon, even on the 
third and fourth day after the beginning of the experiment. 
As the nitrifying organisms had been killed by the ignition 
of the charcoal, nitrates could not be formed. 
These experiments throw little or no definite light on the 
persistence of non-volatile organic poisons in the animal 
body after death. We may perhaps, however, venture to 
assume that as strychnine is decomposed more slowly in 
peat than in gravel, it will prove not less permanent when 
existing in the tissues of the animal body. 
Other questions may be raised concerning the ultimate 
result of the disposal of liquid or semi-liquid putrescent 
matters by irrigation. The experiments described at any 
rate confirm the conclusion drawn from the soakage of cess- 
pools and grave-yards into wells and streams, — that a given 
limited quantity of soil cannot absorb and retain an unli- 
mited quantity of organic matter. 
An important lesson to be learnt from the researches both 
of Emich and of Soyka is that the microbia, both of earth 
and of water, are not necessarily to be regarded as disease- 
generators. On the contrary, we see that certain kinds of 
them are converting malignant matter into forms in which 
it is harmless, or even useful. Hence it is at least possible 
that, even in the application of disinfectants or “ germi- 
cides,” there is room for discretion. 
