The case of the _anopheles_ and his little contribution to human suffering is very different. Whereas the victim of yellow fever either dies or gets better and quickly ceases to be a source of infection to the mosquito, the victim of malaria seldom dies of the disease, but he remains infectious to the _anopheles_ for three years. The disease does not simply attack new-comers or white people. Natives of the isthmus and the West Indies are subject to it, and, indeed, seem to be in a chronically malarious condition. It is said that 50 per cent. of the population of the isthmus were found in 1904-5 to have the parasite of malaria in their systems. It is difficult to estimate or imagine the part played by this widespread malady on conditions of life and civilization within the tropics. Sir Ronald Ross, the greatest living authority on the subject, made some interesting remarks in an address at the Royal Colonial Institute in January of this year. He said:-- Nothing has been more carefully studied of recent years than the existence of malaria amongst indigenous populations. It often affects every one of the children, probably kills a large proportion of the new-born infants, and renders the survivors ill for years; only a partial immunity in adult life relieves them of the incessant sickness. Here in Europe nearly all our children suffer from certain diseases--measles, scarlatina, and so on. But these maladies are short and slight compared with the enduring infection of malaria. When I was studying malaria in Greece in 1906, I was struck with the impossibility of conceiving that the people who are now intensely afflicted with malaria could be like the ancient Greeks who did so much for the world; and I therefore suggested the hypothesis that malaria could only have entered Greece at about the time of the great Persian wars. One can scarcely imagine that the physically fine race and the magnificent athletes figured in Greek sculpture could ever have spent a malarious and splenomegalous childhood. And, conversely, it is difficult to imagine that many of the malarious natives in the tropics will ever rise to any great height of civilization while that disease endures amongst them. I am aware that Africa has produced some magnificent races, such as those of the Zulus and Masai, but I have heard that the countries inhabited by them are not nearly so disease-ridden as many of the larger tracts. At all events, whatever may be the effect of a malarious childhood upon the physique of adult life, its effects on the mental development must certainly be very bad, while the disease always paralyzes the material prosperity of the country where it exists in an intense form.