answer to this is, " Yes and No." As regards the European, it would seem that those who have resided many years in a malarious district are less liable than recent arrivals to severe remittents, but more liable to mild agues. As already mentioned, the first attack of malarial fever is generally remittent and severe in character; subsequent attacks are generally frankly intermittent. Old febricitants are more liable to pernicious attacks of an adynamic type than the recently infected. Trifling causes, such as do not provoke fever in the fresh arrival, are often sufficient to bring on an ague fit in the old resident. The new arrival in the tropics does not think much of exposing himself to the sun, the rain, and the wind; but the old resident is very chary about going out without his sun-hat and white umbrella. The latter wears flannel, and changes his clothes after exercise; he is careful not to cool off too rapidly by sitting in a draught; he will not sit down in wet clothes. The new-comer may look on these precautions against chill as signs of effeminacy. They are not so, however; experience has taught the old resident that neglect of them means an attack of fever and a week off work. The new-comer takes a cold bath; the old resident takes a warm one. The new-comer sits up late, eats and drinks and smokes as in Europe; the old resident goes to bed betimes, and eats and drinks and smokes in moderation. By and by, sharp lessons teach the new-comer to respect the sun and the rain and the wind, to clothe with a view to avoiding chill, and to live temperately. This is an education all pass through in malarial countries. "Acclimatization," to a great extent, though not entirely, means experience, education; not simply an unconscious adaptation of the physiology of the individual, but an intelligent adaptation of his habits.
Racial and individual differences of susceptibility.—— Nevertheless, there can be no doubt that, for some occult reason, certain races and certain individuals are less susceptible to malarial influences than others. A very few individuals are absolutely immune and can live in intensely malarial places with impunity. It is a
