Insects and Disease 
619 
in the blood-corpuscles, using up their substance and breaking them down, 
must work much harm to the human body. This harm is exactly that which 
we recognize as the result of malaria. The fever and other ills that are a 
part of malaria are the direct and indirect pathological effects of the growth 
and metabolism and multiplication of the Haemamoebae in our blood. From 
a single infection the sporulation or escape of the myriads of spores from the 
breaking-down corpuscles into the blood-plasma takes place practically simul¬ 
taneously and makes the beginning of the malarial spasm. This kind of 
multiplication of the Haemamoebae, by sporulation, is termed asexual; there 
is no participation of individuals of two kinds, or sexes, in the reproduction. 
It is a sort of multiplication common to a great many minute, simple animals 
and plants, but it does not seem in any of these to be the only mode of mul¬ 
tiplication. Scores, even hundreds, of successive generations may be pro¬ 
duced asexually, but finally there occurs another kind of reproduction, which 
has for its essential characteristic the meeting and fusing of the nuclei or 
parts of them, and sometimes the body protoplasm or parts of it, of two- 
individuals of the species. In all but the very simplest organisms these two 
conjugating individuals differ somewhat in size, shape, and manner of behavior. 
Scientists began to ask when and how and where conjugation occurred in 
the Haemamoebae of malaria; their questioning was made more insistent by 
the discovery that some of the amcebulae in the blood-corpuscles did not sporu- 
late, but continued to circulate in the blood without any particular function 
at all. More than that, it was noted that whenever they were withdrawn 
from the circulation, as when a drop of blood was taken out of the skin with 
a pipette for examination under the microscope, these traveling amcebulae 
would swell up and liberate themselves from their enclosing corpuscle, and 
that some of them would emit a number of long motile filaments; these fila¬ 
ments could be seen lashing about strongly, and often succeeded in breaking; 
away from the parent cell, and darting away among the corpuscles. This 
phenomenon can always be observed in the blood drawn from a malarial 
patient, in from ten to fifteen minutes after its withdrawal from the circula¬ 
tion. What is the meaning of it ? A further insistent question came up at 
this time. And that is, If the Haemamoebae are the actual and sole cause of 
malaria, how do they get from man to man? How is the malaria dissem¬ 
inated ? 
The explanation of the significance of the phenomenon of the formation 
of the motile filaments from amoebulae in blood withdrawn from circulation, 
and the answer to the question as to the mode of transmissibility of malaria, 
are closely connected, and were reached chiefly through the brilliant work 
of Manson and Ross, two English investigators of tropical diseases. Espe¬ 
cially interesting is the work of Ross in establishing the actual fact of the carry¬ 
ing by the mosquito of the Haemamoebae from man to man. The following 
