36 
EXPERIMENT No. III—Tank Polluted, I-5-11, 4 p.M.—(contd.) 
Surface sample I c.c. 8 A.M., 3-5-11, absent. 
Bottom bs 3 “1 ; present, 
Surface 5 fe »,  4-5-11, absent. 
Bottom és rs 9 5. | SPReSseut. 
Surface ¥ iS is 5-5-11, absent. 
Bottom se =e a %  preseniz 
Surface Jy Seng dee: ,,  6-5-11, absent. 
Bottom 
From both these sets of experiments (1 and 2), it may 
be concluded that natural streptococci die out with great 
rapidity when they are placed in water. The experiments 
also show that they sink to the bottom, where they are 
evidently in very uncongenial surroundings, for they perish 
very quickly. A study of the varieties of the streptococci 
which have been recovered from water supplies has not been > 
carried out in this country, for the simple reason that very 
few colonies have actually been obtained. 
From the point of view of the water analyst the signi- 
ficance of the presence of streptococci in any given sample 
is extremely apparent. Streptococci are extraordinarily com- 
mon in feces and extraordinarily rare in water. They die out 
with very great rapidity in the latter. Apparently the sun- 
light has nothing whatever to do with the rate of disappearance, 
for the cocci perish just as fast in a Winchester quart bottle 
in the laboratory, as they do in rivers and lakes. The presence 
of undoubted fecal varieties is proof of the recent and danger- 
ous character of the pollution under investigation. In India 
it is of little use looking for streptococci in ordinary water sup- 
plies, so a negative result does not increase our knowledge of 
the sample very much. Further, in cases of gross and recent 
pollution, evidence of other kinds is usually very conclusive, 
but the finding of fecal streptococci is confirmatory evidence 
of very considerable value. One example of the usefulness 
of the test may be given, viz., during an investigation on the 
Calcutta water supplies some samples of filtered water showed 
strong evidence of pollution of a most undesirable and objec- 
tionable character ; in one case streptococci also were isolated. 
In this instance a highly polluted subsoil water (which prob- 
ably came direct from a leaky sewer in the neighbour- 
