198 DISEASES DUE TO PROTOZOA 



undergoes so many changes that it is hardly desirable to go 

 into detail here. Suffice it to say that it is a body when 

 adult somewhat larger than a red blood cell, full of actively 

 moving granules. The young forms are homogeneous, and 

 are found with the greatest difficulty except when specially 

 stained. They probably get all their granules from the 

 destruction of the red blood cells. Some adult forms have 

 flagella about their wall. The power of producing disease 

 lies partly in their destruction of the important cells of the 

 blood and partly in a poison they produce. The internal 

 organs, especially the spleen, are injured first by the damage 

 of the blood, and secondarily by the extra work thrown on 

 them in trying to destroy the parasites and to remove the 

 pigment which is liberated by the cellular disintegration. 

 A slight immunity remains after an attack. There is a rela- 

 tive racial immunity among the negroes. The cases that 

 do not wholly recover or that have remote recurrences are 

 said to be harboring quiescent parasites in the spleen. A 

 chronic inflammation of this organ often results. 



Diagnosis. The disease is diagnosticated by making fresh 

 or dried and stained preparations of the blood and examining 

 them under the microscope. Should malaria organisms be 

 present, faint, irregular shadows or larger bodies filled with 

 dancing granules are seen in the unstained blood, while in 

 stained smears fairly well-colored parasites containing quiet 

 granules will be found. Animals are not susceptible to human 

 malaria. Monkeys may be artificially infected. No anti- 

 serum or vaccine treatment is possible now. Quinine is a 

 specific, and if properly used will cure all cases. The spread 

 of malaria is checked by preventing the propagation of mos- 

 quitoes. These insects lay their eggs on the surface of quiet 

 water. The young remain at the surface of the water when 

 they require air. Oil is spread upon the surface of the water 

 and all marshes are drained. No increase of the insects can 

 go on if these two things are done. No quarantine of the 

 patient other than screening from mosquitoes is necessary. 



