19
samples were then taken and analysed. The method of analysis followed in this case
is as follows :-
Two separate grams of the earth were weighed out ; one gram was put direct
into a large tube of bile salt lactose broth ; the other gram was put into 10 cc. of sterile
water thoroughly well shaken, the earth allowed to subside to the bottom of the test
tube, and the clear water, amounting to about 7 cc., put into another bile salt broth tube.
These were incubated at 42° for 24 hours, the organisms that grew were plated on the
usual solid medium, namely, bile salt. neutral red, lactose agar, and separate colonies
were put through sugars in exactly the same way as in the water samples. From the
three samples of earth taken, six sets of about 10 colonies each were obtained. Each
of the samples 1, 2 and 3 contained, respectively, 25 . 37, 28 . 04 and 21:53 per cent. by
weight of moisture. In no case was the actual surface soil, that has been exposed to the
sun, taken in the samples, the earth being collected from a depth of something
between 2 and 4 inches.
The important point about these results is that a large number of different
organisms were isolated. :—•
BacillusGrunthal ...
...
...
...
...
...
... 22
,,
,,
,,
,,
,,
,,
,,
Coscoroba
Neapolitanus
...
Acidi Lactici
...
Coli Communis ...
Cloacæ
...
Lactis ærogenes
No. 67 ...
...
No. 101
.
...
...
...
...
...
...
...
...
...
...
....
...
...
.
...
...
...
...
...
...
...
...
...
...
...
...
...
...
...
...
...
...
...
,..
...
...
...
27
2
5
2
4
1
2
1
Bacillus grunthal and bacillus coscoroba undoubtedly predominated, as will be seen
from the above, but bacillus neapolitanus and bacillus acidi lactici, bacillus coli
communis, lactis ærogenes and two unnamed organisms were also present. There was no
particular difference between one sample and another, and practically no difference
resulted from the two methods of treating the sample of earth. The results obtained
are very similar to what we have been accustomed to get from the bacteriological analysis
of sewage itself. This of course is what would be expected. The point to note in
these results is, that a mixture of fœcal organisms was obtained in nearly every case.
In all three samples sporogenes enteritidis were found living in the earth.
Sample (2), Borhampur trenching ground.—The sample of earth was taken
from a trench that was known to have been filled in at least two years previously. The
contents had not been touched since the night-soil had been deposited. Two wet
seasons had gone by. On opening the trench, which was dug in a light clayey marl,
the dark colour of the earth showed that night-soil had been mixed with the ordinary
greyish earth. On examining this sample the only organism that was isolated in
1 cc. was bacillus cloacæ. Sporogenes enteritidis spores were not present.
Sample ( 3), Anakapalle trenching ground.—A trench that was known to have
been filled up at least two years ago was opened up. The ground in which the trench
was cut was sandy clay, and was of light grey colour. On cutting into the trench a
layer of black earth was found. It was entirely free from odour, and resembled fine
leaf mould in appearance. Bacteriological analysis was made of one gram of this dark
material. The only organism that was isolated. was bacillus cloacae. Sporogenes
enteritidis spores were absent.
Sample (4 ) , Nellore trenching ground. —The Nellore trenching ground is situated
on a piece of land surrounded by irrigation canals. The subsoil water is only about
3 feet below the level of the ground. The land has been trenched for upwards of 10
years, but as the demand for manure is very great in the neighbourhood for use on the
rice fields, the trenches are sold every year in March or April, and the black powdery
earth, which is removed from them, is carried away to the cultivated lands. The conse-
quence is that a trench is filled. and emptied about, twice in three years, the night-soil
never remaining longer than 18 months in each trench. Of course the whole plot of
. ground i is absolutely saturated with contamination. But the earth appears to be very
active for it assimilates large quantities of night-soil with great rapidity, and, within
12 months of depositing the fœcal matter in the trenches, it yields a dark mould like
leaf manure, entirely free from all odour.