For drinking water, eucalyptus oil is good, because after killing the larvae it evaporates and leaves no taste in the water. Kerosene may be used for cisterns from which the water is drawn by a tap.

Still better than destroying larvae is the removal of their breeding places. All old flower-pots, broken bottles, and empty tins should be collected in a dust-bin; old tubs should be broken up, small puddles should be drained or filled up with stones and gravel; drains should be made good, gutters on the roof should be seen to, and

so on.

The householder should go round his house and garden once a week and look into every place likely to harbour larvae. Of course, the water must stand for at least a week before it will breed mosquitoes; and such water must be removed or treated with oil at the weekly visit.

In my experience, if all the stagnant water is removed from the premises, the adult mosquitoes inside the house which must have water to drink and lay their eggs in-soon fly away to the premises of more hospitable neighbours.

It is, in my opinion, possible to rid a whole town of mosquitoes by adopting concerted action against them. It is necessary to employ a sufficient gang of men constantly for the purpose of collecting old tins and bottles, etc.; draining and filling up pools and marshes; and 'training' the banks of streams and large bodies of water. In large towns in the tropics this should be done by the municipality; and I have been urging the measure on British Colonial Governments for some years. It is obvious that if in a town which contains, say, a thousand breeding places of mosquitoes, we reduce these to one or two, then we shall also reduce the total number of

mosquitoes in the place by a large percentage. Of course a few insects may wander into the town from outside, and a few may continue to breed in collections of water, such as wells and large lakes, which we cannot get rid of; but these facts need not prevent us from putting a stop to the proliferation of the insects as much as we can within the area with which we are dealing.

As Dr. Harford-Battersby says in Climate-To say that because we cannot get rid of all mosquitoes we should not attempt to get rid of any, is like saying that because we cannot hope to capture all burglars it is no use for the police to arrest any of them, as others may come to take their place.' Mr. Howard, Entomologist of the United States Department of Agriculture, says in his book, Mosquitoes-'After a number of years' experience in fighting mosquitoes, the present writer has come to the conclusion that there is no reason why any community should submit to the mosquito plague.' He adds that at first he thought this would be possible only in places where the source of the mosquito supply is circumscribed; but that he now thinks it possible anywhere where the people take the necessary trouble. Such has been my opinion for years; but it is unnecessary to discuss the question a priori, since the thing has actually been done. In Sierra Leone, Dr. Logan Taylor and Dr. Daniels report that much success has been obtained in this line; and in Havana, Major Gorgas estimates that on an average mosquitoes have been reduced by ninety per cent. There is, therefore, no longer any excuse why municipalities should not keep the towns in their charge properly drained and cleaned; and if in such towns the reader is much pestered by insects coming from outside his own premises I advise him to write and complain.

Apart from the mischief they cause as carriers of disease, mosquitoes are also a terrible plague in the tropics; and every effort should, therefore, be always made to get rid of their breeding places wherever possible. Thus small settlements of Europeans can always afford to keep two or three intelligent native workmen continually engaged on the job; and even single isolated factories can generally do the same thing. It is astonishing how much in the way of draining and filling up pools and of generally cleaning a place can be done even by a few men when kept constantly at work. As a rule a native workman costs only twelve pounds a year, or even less.

For full details regarding concerted action against malaria and other mosquito-borne diseases, as apart from mere personal precautions, the reader should see my little book, Mosquito Brigades; and How to Organise Them. The book contains a full account of the actual work done in Hong Kong, New York, Lagos, Havana, and Sierra Leone.

CHAPTER III

PREVENTION

XI. PREVENTIVE MEASURES

We have seen then that the following facts have been conclusively proved:

1. The malarial infection is carried from the sick to the healthy by certain kinds of mosquitoes. The insects become infected by biting patients with parasites in their blood, and after a week or two are able to inoculate the poison into the blood of those whom they may subsequently bite.

2. In the tropics, the insects generally become infected by biting native children. After being infected they live about the neighbourhood for weeks or months, biting fresh persons every few days.

These discoveries at once enable us to adopt a number of effective preventive measures against infection from malarial fever in malarious places. The same measures (with the exception of the use of quinine) are effective against yellow fever and elephantiasis. They are as follows:

A. Personal Precautions to be adopted by Everyone -Everywhere:

I. The habitual use of mosquito nets.
2. The occasional use of quinine.

3. Use punkahs and electric fans as much as

possible.

4. Avoid sleeping in the houses of natives or near native villages as much as possible.

B. Domestic Precautions to be adopted in Private Houses, Factories, Plantations, Hospitals, Barracks,

etc.:

1. Removal or protection of all stagnant water in the vicinity.

2. Protection of the windows with wire gauze. 3. Segregation.

C. Municipal Precautions to be adopted by Local Authorities in towns:—

1. Constant employment of a Mosquito Brigade for draining marshy ground, and removing puddles, rubbish, and rank vegetation. 2. Enforcement of proper sanitary regulations. 3. Cheap sale of quinine.

4. Public lectures.

5. Selection and treatment of cases of malaria. 6. Publication of reliable malaria statistics. 7. Employment of an efficient sanitary service. The way to prevent recurrences of fever after infection will be given in the chapter on Treatment.

XII. PERSONAL PRECAUTIONS: MOSQUITO NETS

It will be seen that this list of precautions is divided into three groups-personal, domestic, and municipal precautions. The first can certainly be employed by everyone-except in very rare circumstances.