208 THE INDIAN MEDICAL GAZETTE.
(June, 1904.
I then searched another and much larger tank
of the same nature. It is about 80 yards square
and near it is a large cantonment latrine. The
entire surface of the tank, barring a narrow
streak near the windward bank, was covered
thickly with green scum. Nota single mosquito
larva could be found anywhere. This led me to
look into the surface more closely, and I found
that the green scum consisted of myriads of
plants, each of which had two thick round flat
floating leaves with a slender root going down
into the water. The leaves were so thickly and
closely packed that the surface of the water was
completely hidden. It was physically impossible
for a mosquito to reach the water to lay her eggs.
Major Prain, 1.M.8., kindly identified the or-
ganism as lemna minor. Naturally, the question
arose, why were there no larve in the narrow
open streaks of uncovered water by the banks?
The answer probably is, that as these naked
spots are the result of winds, and as winds vary
in direction, a naked spot to-day might be thick-
ly covered to-morrow, and naturally such uncer-
tain waters would not be safe shelters for larvae;
and mosquitos seem to have learnt this from
experience,
To test this, [ cleared certain small areas near the banks of all Jemna, and enclosed them with light floating structures, which were fixed enough to resist the winds—in fact, made experi- mental pools. I was pleased to find in due time plenty of anopheles larva in these pools.
This seemed to prove that lemna acts as a mechanical obstruction to the process of egg- laying, and a very obvious method of prevention occurred to one. Why not deliberately promote the growth of lemna minor in all unavoidable collections of water to prevent the propagation of mosquitoes ? Thus it might turn out that the pestilential green scum, which we have been in the habit of anathematising, is really a boon and a blessing.
At any rate, I recommend its trial, for it appears to be easy aud cheap to manage,
In our Cantonments there are about half a dozen unavoidable tanks, that is to say, tanks which are too expensive to fill up. There they have to stay giving rise to innumerable anopheles, and incapable of thorough treatment. I would recommend planting lemna minor in such.
In the winter, there is another kind of green scum in water-collections, which does not inter- fere with egg-laying. It is found in ditches, hollows and borrow pits after accidental rain. Examining it under the microscope, it consists of millions of small green flagellated organisms which are ever on the move. It would not be expected to have any preventive use, as the water is not sufficiently hidden. Continuing my observations on those two tanks, I find lemna disappears or gets scanty in the winter. Even if this is the usual case, it seems to flourish in the latter half of the year, and thia is the most important time for prevention. I would invite other doctors to investigate the matter aud report.
NOTES ON THE CULTIVATION OF STREPTOTHRIX MADURAE,
By J. W. CORNWALL, M.A., M.D. (CANTAB),
CAPTAIN, I.M.S.,
Professor of Hygiene and Practical Bacteriology, Madras Medical College.
THE credit of being the first to direct attention to the probably fungoid nature of Mycetoma must be given to Vandyke Carter of Bombay, but it is exceedingly improbable that this officer succeeded in growing the fungus,since the pink Chionyphe Carteri, which he was inclined to regard as the causative factor of the disease, was grown from @ specimen bottled in spirit which had been kept for two years in the dissecting room! Vincent in 1892 and Boyce and Surveyor in 1894 appear to have been the only investigators who have recorded their success in growing the fungus up to date from a case of the disease.
The cultures that have been worked with in European laboratories during the last few years have had their origin from one of these.
During the last three years I have made several attempts to obtain a growth from the granules picked out from feet amputated by Capt. Niblock, 1ms., in the General Hospital, Madras, on account of this disease, but I met with no success until! lately.
The causes of failure were contamination of most of the tubes inoculated with pus organisms and the apparent sterility of those granules which happened to be uncontaminated.
I succeeded at length in obtaining the gran- ules free from pus organisms by taking them with every precaution from the deepest of the sinuses of a recently amputated foot and by washing them thoroughly in at least six changes of sterile salt solution before planting them out.
Out of |7 tubes thus inoculated none were contaminated.
Growth occurred in every case on the agar tubes, but potato, hay infusion and glucose agar tubes showed no growth,
Some tubes showed a visible growth after about a month in the incubator, some not till after two months.
In some cases the growth assumed a pink colour, in others it remained a dull white. In
subculture the streptothrix appeared to have-
become accustomed to the agar substratum and grew much more freely, preserving however its characteristics, one of which is to adhere so closely to the medium that each nodule has literally to be dug out with a very stout platinum wire when it is required to transfer it to another tube.
In subculture fluffy, ball-like growths’ were obtained in broth and hay infusion ‘tubes. ~~
