REPORT ON THE WORK CARRIED OUT IN THE MICRO-BIOLOGICAL
SECTION OF THE KING INSTITUTE OF PREVENTIVE
MEDICINE, GUINDY, FOR THE YEAR 1915.
There were no changes in the staff during the year.
Water Analysis. —As in the immediately preceding years no quarterly or half
-yearly routine analyses were carried out, but a very large number of samples were
examined in connection with the Experimental filters at Guindy, the Madras
Corporation filters at Kilpauk, and proposed or extended water works in the
mufassal.
The Guindy Experimental Filters. —A Mather and Platt mechanical filter was
added to the installation. It was however completed too late in the year for any
experiments to be carried out with it. The work carried out was mainly confined
to the comparison between covered and uncovered sand filters. The Clemesha
pattern sand filter was provided with a light roof and to make the experiments
more comparable, the depth of the water over the sand was increased to three feet.
Subsequently side flaps were added to the cover so as to more completely exclude the
light. This was found to be an improvement. An investigation of this nature is
bound to be a prolonged affair, as accurate data can only be obtained by studying
the comparative behaviour of the filters from cleaning to clogging. Three months or
more, during which samples have to be taken and examined daily from both filters,
are therefore required to carry out a single comparison. During the year such
comparisons have been carried out and show conclusively that for Adyar water the
covered filter gives a filtering skin which, for endurance, efficiency and probably
for proportional yield, is definitely better than that formed in an uncovered filter.
Madras Corporation Filters. —At the instance of the Special Engineer to the
Corporation, I paid several visits to Kilpauk and discussed a system of bacteriolo
-gical control of the filters with him. The control of such a large number of filters
was quite beyond the staff available either at Kilpauk or Guindy; so, as a tempo
-rary measure, it was decided to control two filters only and to carry out a series
of experiments as to how a filtering film of reliable and enduring quality could best
be obtained. In addition to being hampered for want of staff, there was, in conse
-quence of the war, a possible want of material to be considered. On this account
also it was not possible to launch out into such a large scheme of work as would
be involved in controlling all the filters. A farther desideratum was a more
rapid test than the usual full analysis. Attention was drawn to this in last year's
report, and the difficulty was met by restricting routine analyses to two points,
namely, the total count and the quantitative estimation of lactose fermenters.
This was found to work well, and, as a good approximation to the final result can
be got on these points in two days, a great saving of time was effected This
enabled the staff to make many more analyses. Analyses in connection with new
or extended supplies were carried out in the usual full manner. To assist in the
Corporation work, Mr. Venkata Rao of the " Filtration Staff " was deputed to the
Institute. He was instructed in sample-taking and in the elementary technique of
plating out and the quantitative estimation of lactose fermenters. In view of a
possible scarcity of material, especially of Witte's peptone, the export of which
from Britain was prohibited, experiments were carried out to see if the medium
elaborated for the preparation of the Plague prophylactic was suitable for the
estimation and classification of lactose fermenters. A quantity of this medium
was kindly sent from Parel by Major Glen Liston, C.I.E., I.M.S. It was tested
against a large number of lactose fermenters isolated from Madras water supplies
and was found to answer well. This will result in a considerable saving especially
in connection with large scale routine control analyses.
An examination of a very large number of results of bacteriological examina
-tions conducted during this and previous years leads to the conclusion that in some
way or other sand filtration exercises a selective action on water bacteria and that