_Prophylaxis._—Only those preventive measures which can be put into operation by the individual will be here considered. This may be called _personal prophylaxis_. By far the most important means of avoiding malaria is the proper use of an efficient mosquito net. The oblong type is best, and it should contain sixteen meshes to the linear inch. Round the foot of it should be sewn a stout layer of calico 2 feet in depth. This will permit of a foot of the material being tucked under the mattress while the upper foot remains in the form of a belt or zone round the bed. It is necessary, because in its absence the sleeper is very liable to be bitten through the mosquito-net mesh, with which his arms or legs are apt to come in contact. Care must be taken to see that the net is kept in good repair—a most important matter—and in very malarious countries it is advisable to provide every member of an expedition, native or otherwise, with a good mosquito net. In what may be called the dry tropics, the top of the net may be of mesh; in the moist tropics, it is best made of calico in order to keep off the heavy dews. The traveller often sleeps out on the deck of river steamers, and then it is certainly advantageous to have the roof of the net composed of stout calico, as sparks from the funnel are very apt to alight upon it, and naturally holes will be burnt much more readily in mesh than in thick cotton. It is foolish to sleep even for one night in a malarious locality unprotected by a net. The net is for use during the period of sleep, but one is very apt to be bitten by infected mosquitoes just after sunset, and hence it is well to make use of some form of mosquito canopy. A good type is the so-called mosquito umbrella tent. Such a canopy may be arranged so that the evening meal can be taken in it. One servant will be inside the canopy and receive the dishes through a guarded opening from the attendant outside. Other methods of protection exist in the shape of mosquito boots or buskins. The best type of mosquito boot is the form which reaches right up the thigh. They may be made of untanned leather or of stout khaki cloth. All mosquito boots and buskins should be provided with soles to protect the feet from wet and damp. In the absence of boots it is well to know that a mosquito will not bite through two pairs of stockings, one super-imposed over the other. This is a way in which women can protect their legs and ankles, or they can employ the buskin, leggings, gaiters, or puttees. Mosquito veils have been mentioned, the best type being the “Mosquinette” hood. Mosquitoes are apt to bite through chairs with cane seats or with perforated seats, and these should be guarded by a layer of brown paper, newspaper, or a cushion. Repellent substances may be used, smeared on the skin. They contain essential oils, such as oil of cassia or eucalyptus oil. These repellents are effective only for a short time, but lessen in some degree the liability to infection.