MALARIAL PARASITOLOGY 513 



The smear is dried without heat and held for a second or two in 

 the dye. It is then dipped slowly into a vessel with clean water, film 

 Me down; it should not be plunged into the water. The staining 

 depends upon the interaction of the water with the film of dye adhering 

 to the blood. Hold preparation in the water for a few seconds, then 

 move it about for a moment, and rinse in clear water; clean lower side 

 of the slide, as precipitation will have taken place here; hence, do not 

 introduce into water with film side up. Dipping the preparation for 

 a moment into 50 per cent, ethyl alcohol removes smudges and pre- 

 cipitate. 



Mode of Infection. While it is probable that infection with malarial 

 sporozoites occurs in the great majority of cases by the bite of an 

 infected mosquito, there seem to be cases in which the infection has 

 taken place in some other way. Mosquitoes normally feed on plant 

 juices; to obtain their food they insert their proboscis into the plant 

 tissues. Is it then unreasonable to suppose that such a plant would be 

 infected in a manner analogous to the manner in which the human 

 blood is infected? Why should not such a vegetable eaten uncooked 

 cause an infection through the gastrointestinal tract? Again, infected 

 mosquitoes after ovipositing may die in the water, and, partaking of 

 such water, might lead to infection; or if the insect died in the open air 

 the sporozoites might be carried by air currents and infect through the 

 respiratory tract. 



The fact that with the extermination of the anopheles varieties mala- 

 rial fevers in man would be made impossible remains established; the 

 parasite must have its chance of rejuvenescence in the mosquito's 

 stomach. 



Hitherto no experiments have been made to show the possibility of 

 sporozoites penetrating the capillary walls of the lung tissue or those 

 of the mucous membranes. 



Malarial-like Organisms in Other Animals. Two varieties of malarial 

 parasites have been found in birds, the proteosoma (Hcemamoeba 

 relicta, Cytasporon danilewskyi) and the Halteridium (hsemoproteus). 

 The development of each seems to be very similar to that of the human 

 malarial organism. The life cycle of the proteosoma is the better known 

 of the two. The asexual cycle, or schizogony, is best studied in artificially 

 infected birds (canaries). The sexual cycle occurs in the gnat (Cidex 

 pipiens). 



Conjugation of malarial organisms was first observed by MacCallum 

 in the genus Halteridium in birds, and his discovery gave the first clue to 

 the nature of the flagella. 



-Malarial-like organisms have also been found in monkeys, cattle, 

 and frogs, but they have not been minutely studied. 



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