[413] 
BIOLOGICAE 
eee D Ye OE OE ET Ee AV A ES ER 
IN THE SCHOOL OF PRACTICAL SCIENCE, TORONTO. 
BY GEO. ACHESON, M.A. 
Science Master in Toronto Collegiate Institute. 
The object of this paper is to give the results of investigations 
into the biological nature of the suspended matter in the tap-water 
of the School of Practical Science. No pretence is made of being 
exhaustive, for the work has only been carried on at intervals, and 
observations for any definite length of time have not been continu- 
ous. The results therefore are fragmentary, but may serve as a basis 
for future and more extensive research. A thoroughly systematic 
examination of the water should include not merely the determina- 
tion of the animal and vegetable species which are to be found in it, 
but the physiological influence which these organisms exert, and 
their importance from a sanitary standpoint. This subject accord- 
ingly may be dealt with from both a morphological and a physio- 
logical point of view. t is with the first of these aspects only that 
the present paper is concerned. In regard however to the physio- 
logical and hygienic aspect it may be briefly observed, that the 
purity of water does not depend merely on the quantity of organic 
matters which it contains ; for, if these be living vegetable growths 
containing chlorophyll, they have a beneficial influence on the water, 
by supplying oxygen to it and removing carbon dioxide, provided, of 
course, that their presence in large quantities does not counterbalance 
their salutary effects. On the other hand, there are organisms 
which, even if present only in smail numbers, exert a very prejudi- 
cial influence, and which, if undoubtedly recognized as constantly 
occurring, should mark a water as unfit for use. 
To obtain matter for examination two methods may be employed. 
One is to tie a muslin bag to the tap and allow the water to run in 
a slow stream for a few hours; then, taking off the bag, rinse it in 
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a small quantity of water, which, on being allowed to settle for a 
