Insects and Disease 
617 
cared for in the isolation hospital, which is now closed. The benefits of the 
war waged on the mosquito at Rio Janeiro have been as great as those obtained 
at Havana, where the vigorous work of the American authorities during our 
occupation of the islands practically stamped out yellow fever in a city long 
notorious the world over as a plague-center. 
Mosquitoes and malaria. —First of these known cases of the dissemina¬ 
tion of human disease by insects to be worked out in detail was the relation 
of mosquitoes to the breeding and distribution of the causative germs of 
malaria. Malarial fevers occur the world over and have long been associated 
in the popular mind with low wet localities or with localities near marsh 
or swamp. Mosquitoes live in great abundance precisely in such regions, 
but for a long time no association between mosquitoes and malaria was 
even suspected. Miasma, the effluvia from low wet ground, was held to be 
the causative, or at least carrying, agent of malaria. It was not until 1880, 
when Laveran discovered and described the actual parasitic sporozoon 
(minute one-celled amoeba-like animal) of malaria, that the actual cause of the 
disease was recognized. 
Malaria as we know it in the United States is a wide-spread and serious 
disease, but not commonly a fatal one. But in India five million deaths 
occurred in a single year, 1897, from malarial fever. Giles declares that the 
malarial parasite is responsible for by far the greatest proportion of all sick¬ 
ness and death in the tropics. “Cholera and plague,” he says, “are the 
insignificant enemies that perhaps kill a few thousands a year—in an impres¬ 
sive way, it is true; but the quiet insidious malaria sweeps off its millions.” 
The serious state of affairs in India, as well as on the Gold Coast of Africa, 
■on the Roman Campagna, and in other notoriously malaria-stricken regions, 
finally led to careful scientific study of the life-history of the malaria-pro¬ 
ducing sporozoon by well-trained English and Italian physicians and natu¬ 
ralists, with the result that we now know in definite and accurate detail the 
whole marvelous story of the interrelations of the malarial parasite, the 
mosquito, and the human host. 
Lankester was the first to find an amoeba-like parasite living in the blood 
of animals, Drepanidium ranarum of frog’s blood, but since his discovery 
numerous other similar protozoon blood-parasites, collectively called Haema- 
tozoa, have been found in reptiles, birds, bats, cattle, and monkeys. The 
haematozoon infesting cattle discovered by Theobald Smith, an American 
investigator, produces the disease known as Texas fever, and is spread from 
animal to animal by ticks. The particular blood-parasites, called Haema- 
mcebae, which produce malarial fevers, are not restricted to man alone, but 
infest birds, bats, and monkeys as well. 
In 1885 Golgi discovered that the malaria-producing Haemamoebae of the 
human body exist in three varieties, each apparently responsible for one 
