MICROSCOPICAL EXAMINATION OF WATER. 587 
identical in appearance and character with those which were 
produced by the addition of fresh urine to a portion of the 
same water, and it was difficult to comprehend how, when 
fresh urine was used, one class of the organisms developed 
corresponded with those produced in the presence of phos- 
phate of lime, while the filament was absent. 
To try and assimilate more the conditions of making the 
experiments with a phosphate and the urine, I added very 
minute quantities of phosphate of potash to New River 
water — from two to five hundredths of a grain to 40 ounces — 
and with this proportion of phosphate a beautiful filamentous 
development similar to that which was produced by the one 
drop of urine, made its appearance, thus clearly indicating 
that phosphate of lime exercised an important part in causing 
the development. 
I next largely diluted some water that had been filtered 
through animal charcoal, and subjected a portion of the mix- 
ture of filtered and unfiltered water to the sugar test, when 
an abundance of fine filaments was developed. These filaments 
were not identical with those produced in the presence of 
urine ; but the difference was probably due to my not having 
arrived at the proper conditions. 
From what has been stated it will be seen how easily by a 
slight change of conditions the line of development of living 
things may be modified, and this is one of the great diffi- 
culties to be contended with in attempting to establish 
whether a water is impure or not, from the development 
therein of any particular organism ; and it is even possible 
for a water under certain conditions to contain combined 
nitrogen without producing, when submitted to the sugar test, 
any turbidity. 
Dr. Frankland, whose researches on this subject are full of 
interest, was the first to make the observation that effluent 
sewage water, when passed through a thick bed of gravel, 
was deprived of its phosphates, and that although containing 
combined nitrogen, the water, when submitted to the sugar 
test, remained bright. 
I was unsuccessful until within the last few days in obtain- 
ing any filamental growth from vegetable albumen approach- 
ing in appearance the filaments that occur in water containing 
sewage. A small quantity of partially purified vegetable 
albumen was introduced into New River water contained in 
an open glass vessel and left for nine days, at the expiration 
of which time the water contained filaments, both in strings 
and fragments, the latter being almost undistinguishable from 
those found in effluent sewage waters. 
