FxVMILY CULICID.E THE MOSQUITOES 89 



remain in tlie red blood cells, no further development taking place. 

 From this point on the mosquito becomes an essential factor since, unless 

 they are ingested by a mosquito, the gamctocijtes are capable of no 

 further development. 



When the gametocytes are taken into the mosquito further develop- 

 ment occurs, commencing in the stomach of the host. The female 

 {macrogametocytes) mature into what is called a macrogamete, corre- 

 sponding to a ripened but unfertilized ovule, while the microgameto- 

 cytes give off a number of thin, elongate, worm-like bodies, the male 

 elements or microgametes. These travel about by a lashing motion until 

 they come in contact with a macrogamete, when they penetrate the cell 

 wall and fertilization takes place, producing a zygote, a round body 

 which soon elongates into an ookinete which becomes active, penetrates 

 the wall of the stomach and establishes itself between the epithelial and 

 muscular layers. In this position it absorbs food from the surrounding 

 tissue, becomes spherical and very large, and in this stage is termed 

 an oocyst. In this stage the spores (corresponding to eggs) are de- 

 veloped, and arc called sporozoites. They escape by the breaking of the 

 oocyst and enter the body cavity, where they are carried to all parts of 

 the body by the free-flowing blood, many of them finding their way to 

 the salivary glands and into the blood streams of human beings where 

 they penetrate the red blood cells and develop into schizonts. 



It will be seen from this that the sexual stage occurs in the mos- 

 quito, occupying from eight to fourteen days, and probably results in 

 no ill effects to its host, since it is a cold-blooded creature. 



In tertian malaria a chill is produced about every three days, fol- 

 lowed by fever, while in quartan malaria the chill occurs every four 

 days, due to the longer incubation period of the merozoites, while in 

 pernicious malaria the chills and fever are irregular. 



Blackwater Fever is now believed to be the result of numerous 

 attacks of malaria or a more or less continuous infection and derives 

 its name from the fact that the patient's urine is of a dark mahogany 

 color due to the presence of broken down red corpuscles. 



Yellow Fever may be carried by at least three species of mos(iuitos 

 in America Acdes (Stegomyia) aegypti, Avdes fluvialtilis and Aedes 

 scapularis. Possibly other species might carry the disease as well but 

 we fortunately do not have it in the United States, even though 

 A. aegypti is common in the south. With present facilities for rapid 

 transportation there is danger of travellers from yellow fever areas 

 entering the country and developing the disease after arrival. If we 

 were sure that the disease would be quickly diagnosed and the patient 

 isolated in a mosquito-proof room we misfht feel much more certain 



