50 



ANIMAL BIOLOGY 



At length these spores escape through the outer wall of the 

 mosquito's stomach and many of them find their way to the salivary 

 glands. And so when the infected mosquito bites another person, 

 these parasites are injected with the saliva, and if the conditions are 

 favorable in the blood of the new victim, the spores straightway 

 attack the red corpuscles, and a new case of malaria is the result. 



For the treatment of malaria quinine is the most effective drug 

 known at present. It should be taken in the quantity and at the 

 times prescribed by the physician. 



malaria parasite enter- 

 ing a red blood cor- 

 puscle and develop- 

 ing 13 new parasites 



stomach of a mosquito 

 with swellings filled 

 with malaria spores 



! malaria spores from 

 salivary glands of 

 mosquito (much en- 

 larged) 



FIG. 33. Life history of the malaria parasite. (Dahlgren, American 

 Museum Natural History.) 



41. Transmission of yellow fever. The proof that malaria can 

 only be transmitted from one human being to another was largely 

 the work of the biologists of England, France, and Italy. The dis- 

 covery that another kind of mosquito (Stegomyia) is responsible for 

 the transmission of the parasite that causes yellow fever is due al- 

 most wholly to the splendid achievements of the Yellow Fever Com- 

 mission appointed by President McKinley. In June, 1900, this 

 commission of five, headed by Dr. Walter Reed (Fig. 34), began its 

 epoch-making experiments in the Island of Cuba, and within six 



