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Page:Popular Science Monthly Volume 81.djvu/51

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mitting this disease, it remained for Dr. Patrick Manson, of London, to point out in 1895 that the malarial parasite had an alternate mode of generation, and he considered some blood-sucking insect (probably a mosquito) as the most probable host. His pupil, Dr. Ronald Ross, an English military surgeon, soon went to India, and after patiently dissecting the bodies of hundreds of mosquitoes, finally discovered one having pigmented bodies in the stomach after biting a malarial patient. In 1900, Sambon and Low, and Grassi, conducted in the most malarious sections of Italy careful experiments which proved to the world that malaria is transmitted to man through the bites of the malarial mosquito, Anopheles maeulipennis. These experiments have since been duplicated and the results confirmed by many others in different parts of the world.

Mosquitoes breed only in water,-and the malarial mosquito will breed in almost any pool where other kinds flourish, but is never so abundant as the rain-barrel mosquito, Culex pipiens, or the salt-marsh mosquito, Culex sollicitans. It lays its eggs singly on the surface of the water. They hatch in a few hours, and the young larvæ or wigglers feed in the water on minute particles of vegetable matter. Each larva goes to the surface every few minutes to inhale air through the tube or siphon near the tail. In a few days the wiggler changes to a peculiar hunchback pupa, and the adult mosquito emerges two or three days later. Only a week is required in warm weather to complete the life cycle.

As a rule, mosquitoes do not fly far, and usually breed in the vicinity where they occur. The salt marsh mosquito is an exception to this rule, and often flies inland for twenty-five or thirty miles, though it breeds only near the coast.

From the records of the State Board of Health it appears that for the decade ending with 1903, 1,073 deaths, or more than 100 each year, occurred in Connecticut from malarial diseases alone. Dr. Howard obtained similar figures from those states where statistics are kept (less than one half of the states keeping them, and these being in the north), which show that more than 12,000 deaths occurred in eight years from malaria. From the records of a number of cities it appears that two deaths occur from malaria in the south to one in the north, and on this basis and including the non-registration states, he concludes that the annual death rate from malaria in the United States must amount to 12,000, and that it would be 96,000 for the eight-year period.[1]

But with malaria perhaps more than with any other disease the death rate is a small indication of the economic loss suffered. Many

  1. L. O. Howard, "Economic Loss to the People of the United States through Insects that Carry Disease." Bureau Entomology, Bull. 78, p. 10.