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The first three methods are most costly, take a long time to apply and are generally slowly brought about by the different trades which develop in a country.

They are quite unsuitable for immediate or for Governmental application. The cost to drain a single large swamp would be enormous. Moreover, it is quite impossible to do away with rice fields in Ceylon.

I therefore propose to exclude those from practical application and to let them come about gradually by trade development.

But under head 4 the removal of small pools, much can be done. If compounds round houses were kept clean, and no small green pools allowed to remain undisturbed, if no small ponds were allowed in such compounds, or in villages and towns, then a great means for the mosquito to propagate its species would be destroyed.

This is practically a piece of sanitation.

In-very malarious districts, compounds should be kept clean, no duck ponds, &c., allowed, and small ponds in the centre of towns and villages should be filled up. From my observations there is not the same difficulty in doing this in Ceylon as there was in West Africa.

In Ceylon there are wells with good water and as a rule the people do not depend upon open small pools for their drinking and other water, but in West Africa they did, and if those pools were filled up, say in Accra, the people would have to carry water several miles, for the well water of that town is brackish.

Sanitary, legislation might prevent new houses being built near rice fields or new rice fields in close proximity to existing houses, villages or towns.

(B) The Destruction of Larvae :-

—

The different methods for the destruction of larvae may be classified as follows:-

1. Destruction by other animals and larvae introduced into swamps, pools, &c. 2. Destruction by chemical means.

3. Destruction by mechanical means.

4. Destruction by sanitation.

1.-Destruction by other animals and larvae introduced into swamps, pools, &c. In certain swamps in Colombo in which live large numbers of a small fish with a silver ring behind the head, I have been unable to find the larvae of mosquitoes. While only a few yards away there were pools which did not contain this fish and there culex and other larvae were found in abundance.

Unfortunately it has been found that the introduction of fish and larvae of other insects has not been very successful, therefore I should not suggest the trial of any such scheme, for it would involve the building of tanks to keep the larvae of these fish till ready to be despatched to a given destination and also the expense of caretakers,

&c.

2.-Destruction by chemical means:-

Numerous chemical reagents have been employed in the attempt to kill the larvae. 'Chemicals placed in water are, in my opinion, dangerous and expensive, and are not suitable for use on a large scale.

3.-Destruction by mechanical means:-

This really means destruction by spreading some oil on the surface of the water and thereby preventing the larvæ and nymphae from obtaining the air necessary for their existence, as they cannot breathe through the oil film.

It certainly does do this, and is valuable in small collections of water full of the anopheles, e.g., it is being used for the little stream at Polgahawella railway station mentioned in Part I, Section IV., but it is impossible to apply it on a large scale to the swamps, paddy fields, &c., of Ceylon.

But still it is useful in individual cases and for that purpose it should be used. Experiments have been made with regard to the spreading powers of certain oils by Dr. Kohn of University College, Liverpool, and he finds that the best and cheapest arc either crude petroleum (film lasts 10 days) or crude creosote.

4.-Destruction by sanitation:—

If canals were cleaned out, small pools of water were cleared away from the neighbourhood of houses, by filling up or emptying into drains, and if drains were kept clean so that water flowed rapidly through them instead of stagnating, then a number of excellent' rearing grounds for larvae would be destroyed, and the larvae with them.

2. Those applied against the life and presence of the mosquito:- Many are the ways in which it has been advocated that the mosquitoes can be driven away or killed. Chrysanthemum cones burnt to produce fumes, kajhu nut,

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burnt by the natives of Ceylon as previously described, also mathuru thala kola, cocoanut, handung kuru, kata kumangjal.

Agreeable and disagreeable odours have all been tried, e.g., oil of rue. Tobacco smoke has been advocated. The ordinary burning of sulphur will, of course, kill mosquitoes.

None of these methods appear to me to be applicable on a large scale. Moreover, they take a very long time to act, except sulphur.

B.-Those applied to Man.

These may be divided into:-

1.

Education as to the cause of malaria,

2. Mechanical appliances.

3. Secondary matters, drugs, food, clothing. 1.-Education as to the cause of malaria :-

Sce Part II, Sections VI and VII. 2.-Mechanical Appliances:- These may be sub-divided into—

(A) Gnat proof dwellings.

(B) Mosquito curtains.

(c) Protection when out at night. (D) Artificial Ventilation.

(A.)-Gnat Proof Dwellings:-

These must be considered according to the class of people who live in the dwel- lings; it will be necessary therefore to consider them under the heads of the three Classes defined in Part II, Introduction.

Class I.-Bungalows could be readily built having verandahs completely sur- rounding the house and the boys' quarters, the latter being connected by a covered passage.

The arches of such a verandah should be closed by copper wire netting so arranged) that it can be withdrawn aside in the day time and placed in position about one hour before sunset.

This can be done by the door or the shutter system.

A bungalow fitted in this way is shown in Figure XXIV., all ventilators and thẻ

kitchen chimney must be closed in the same way.

It is necessary to have the verandah all round, and to enclose the kitchen and boys' rooms in order that there may be no exposure to infection while serving dinner at night,

&c.

The good points in this method are:-

(1) It is cheap.

(2) It can be applied to many existing bungalows.

(3) It enables all the doors and windows to be left open at night if desired, and

consequently it does not increase the heat in the bungalow.

(4) Persons residing in such a bungalow are not merely protected against mos-

quitoes, but against all kinds of flying insects.

If the bungalow is already built without a verandah all round, then these doors

and windows on the side or sides without the verandah should be closed with copper wire netting as well as with ordinary glass windows.

These gauze windows should be placed in position one hour before sunset. Class II-Windows, chimneys, and doors should be closed with copper gauze, which could be placed in position before sunset,

Class III.-Nothing can be applied to the dwellings of these people who will be considered under the next section.

(B) Mosquito Curtains:-

These would not be essential if the people lived in gnat proof houses. In other houses they should be used and should be of proper mesh and size; vide Figure XXI.

When torn they should be at once mended.

They should be placed in position long before sunset.

(c) Protection when out at night:-

Natives do not work at night. Suitable mosquito veils and gloves can be advised

to be used by anyone compelled to work at night in the open air in very malarial places.

(D)—Artificial ventilation :-

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