As, however, it is not always possible or convenient to incur the delay of boiling the drinking water and allowing it to cool, it is advisable that a reliable filter should be taken.
Most filters—charcoal or otherwise—are merely death-traps, as the accumulation of germs and injurious matter within the filtering substance soon renders the water more dangerous than if unfiltered. There are, however, a few filters which, with ordinary care in cleansing, are in themselves efficient safeguards. The most highly recommended of these are the Pasteur Chamberland and the Doulton filters. In any case, spare filtering candles should be taken, and these should be cleaned and boiled at least every three days. It is recommended that the filter-makers should be consulted immediately the probable requirements of any expedition are known. It should be remembered that no filter combines rapid delivery of water with efficient sterilization. A mistake commonly made is to boil water and then filter it. This should never be done.
The drinking of very cold water, to which there is great temptation when one is exhausted by prolonged heat and copious perspiration, should be carefully avoided; thirst often induces tropical residents to have recourse to iced water, which is always apt to be dangerous if taken when one is heated. The drinking of copious draughts of water is also a habit to be deprecated; it certainly weakens the muscular energy, and as the water is rapidly lost by perspiration, the feeling of exhaustion is increased. Hot or cold weak tea, without milk or sugar, is one of the least injurious of all beverages.
Precautions on the Voyage.
The traveller should endeavour to land in a perfectly healthy condition, and to this end he should on the voyage out take plenty of exercise, drink little or no alcohol, be moderate as to diet, and avoid much meat and rich dishes. Neglect of these obvious rules frequently ends in the traveller arriving in a flabby, bilious condition, in which state he is predisposed to attacks of malaria, dysentery, and other diseases.
Constipation is frequent at sea, and a seidlitz powder, a dose of fruit salt, or one or two cascara tabloids may be necessary. If constipation is severe, then one or two four-grain blue pills should be taken at bedtime, followed in the early morning by a seidlitz powder or some other saline aperient.
In order to avoid chill the traveller should be properly clothed during the evening or when there is a cool breeze, and should not stand in draughty doorways and passages on board. If he is proceeding to a country where there is endemic malaria he should begin his course of prophylactic quinine on ship-board, because even a single night spent ashore in a malarious locality may result in his acquiring infection. It is therefore advisable to begin taking quinine in the manner described on [p. 207] at least two days before arrival at the place of disembarkation.
What is true of the journey out is of even greater importance on the voyage home. There is a serious danger of illness owing to chills contracted on board ship when leaving a hot climate. Quinine should be systematically taken as recommended on [p. 208].
General Hints.
Never take a cold bath in the Tropics unless ordered to do so by a doctor.—In the case of persons who have already suffered from many attacks of fever, dysentery, or any disease of the liver or other important organs, warm bathing should alone be used. Bathing should never be resorted to during the period of digestion, i.e., three to four hours after meals. Wear warm clothes at night. Avoid the direct rays of the sun. Do not take too much animal food. Never begin work on an empty stomach. Never neglect a slight attack of fever or diarrhœa. Keep the bowels gently opened—once a day is quite enough—but avoid strong purgatives.