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ber, is practically stationary in December, and markedly increases in January. It will also be noticed that there is a second much smaller rise to a maximum in July. This rise begins in June, reaches its maximum in July, and falls to a minimum in September. The great rise starts in October, reaches a maximum in January, and falls to a minimum in May.
When an enquiry is made into the cause of these rises, it is found that two diseases are mainly responsible, viz.:
(1.) Malaria.
(2.) Dysentery.
Y •
If Chart II. be now examined it will be at once noticed that the curve of 1899 is very similar to that of the general curve of disease. The rise began in October, reached its maximum in January, fell till April, rose again to a slight maximum in September. In 1898 the maximum was lower than 1899, and was in December instead of January. The rise began in June and was continuous.
1
When the mortality is considered, Chart III., it will be seen that the total deaths at institutions from all cases is similar in the two years. In January the maximum is reached for 1899-then a fall till April, a second rise to a maximum in May, and fall after July to a minimum in October. In December, 1898, the maximum for that year is reached.
When the mortality curve for Malaria alone is examined, Chart IV., it will be seen to be singularly like that of Chart III.
Conclusion.
Malaria is a powerful factor in the disease and death rates of Ceylon.
III. The relationship between Malaria and the Rainfall.
When the diagram of the rainfall for the whole Island of Ceylon is examined, it will be seen that there are two minima, one in February and one in August.
But this method of considering the rainfall is not quite satisfactory, for as has been pointed out to me by Dr. Fernando, the Island may be roughly divided into two.
(1) A Western-affected by the South-West Monsoon. (2) An Eastern-affected by the North-East Monsoon.
Of the Western towns I have only at my disposal the rainfall of Colombo. If attention be now turned to Chart VI. the rainfall will be noticed to reach two maxima, one in May and one in October. If now Chart VII., the number of Malarial cases in the West, be examined, the highest points of the curve will be found to be in June and in January, that is after the highest points of the rainfall, and it will be noticed that the rise in the cases of disease may begin just before and continue after the rise and fall of the rain curve respectively.
In Charts VIII. and IX., a very similar curve will be found, except that the secondary rise is not so marked in the rainfall as in the Western District.
These two charts are not drawn to the same scale, owing to the enormous relative rise in December, which would have rendered them of large size if made to the same scale.
over,
The most marked increase in the malaria is directly after the maximum of the rainfall curve, and it keeps at a high level till the secondary rise in May consequently a secondary rise does not take place in its curve. It drops to a minimum in August which is also the minimum of the rainfall.
Conclusion.
There is, therefore, a definite relationship between malaria and the rainfall.
Examination of the Relationship between Malaria and the Rainfall.
•
There appears no doubt that the reason why so few, sometimes no, anopheles are seen in the dry season for months together, e.g., in Accra and Kumassi, West Africa, and then the sudden appearance of these insects in numbers is due to their hibernation in dark protected spots. They come out again in the wet season, as this is the time, par excellence, when they find the pools of water with suitable algae for propagating their species, and in my opinion this is the reason of the relationship between malaria and the rainfall.
IV. The Anopheles and its Haunts.
Up to date of writing I have not had very much opportunity of studying the
53
anopheles and its haunts in Ceylon, but the few observations which are here recorded will, it is hoped, be much extended in the course of a few months.
The anopheles which I have found have resembled, but not quite exactly, Anopheles Vanus.
Another anopheles is an undoubted Anopheles Rossii.
Another, Anopheles X, has costal margin of the wing decorated with two white spots. One very small the tarsi banded and the abdomen with a darker kind border to the segments.
In Colombo anopheles have mainly been found in Borella district, but are not very abundant, and though a number of specimens have been dissected none of them were found to contain any malarial germs.
The larvæ have been found in small numbers from time to time in pools, dg., Victoria Park. Figure X.
in
Anopheles X was found at Kurunegalle (a Malarial district) and the larva were found abundantly in the paddy (rice) fields near the hospital and the station. Figures XI and XII.
In Polgahawella, which is a marked malarial station, there were a large number of larvæ in a small stream which issued from a low tunnel under the railway line. This stream after passing through the tunnel stagnates close to the platform, and is there covered with green algae, and it was in this part that large numbers of larvæ were found. Figure XIII.
It was observed that no larvæ were to be found in pools which, though otherwise apparently suitable yet contained a little fish with a silver ring.
There has been a severe outbreak of malarial fever in Katancudy, and from there two anopheles were sent to me, one of which was an Anopheles Rossii, and the other, much damaged, probably Anopheles Vanus.
The Medical Officer, Dr. Hallock, acted with great discernment, and by promptly cleaning the village made at once a marked effect in the disease.
In so doing I feel sure that he removed a large number of anopheles larvæ, which would be living in the little pools.
Such, I am sorry to say, is the very imperfect account which at present I can give of the anopheles in Ceylon.
Ceylon appears to me peculiarly suitable for the development of anopheles. There are large numbers of shallow stagnant pools with plenty of green vegetal matter. There are heavy rains and there are in fact all the requirements for the life of a mosquito.
There are plenty of anopheles and various culicidae, but there appears to be a comparative scarcity of the malarial germ in the anopheles; which is different from West Africa where the germ was common,
V. The Investigation of Malarial Localities.
Malaria is not equally prevalent all over Ceylon, nor at all seasons of the year in the same place.
The marked malarial places are well known, but in order to study the malarial fevers of a given place with a view to its prevention a definite system must, in my opinion, be adopted.
This is the more necessary as it might possibly be found that malaria was not as common as the statistics show.
The main points to be observed in the investigation of a district in which malaria
is very prevalent are these:-
1. What is the nature of the fever?
2
Are the attacks primary or secondary? •
•
3. What are the kinds of anopheles in the district?
4.
Which of them contains the "malarial germ?
5. Where do their larvæ live?
6. What is the relation of the epidemic to the rains, &c.?
7.
What are the habits and customs of the people?
1. What is the Nature of the Fever?
This can only be determined by microscopical examination, and the methods to
be adopted will be dealt with under Part II, Section VII.