DAHLGREN, THE MALARIA MOSQUITO 



37 



Sexual forms 

 of the Parasite 



when removed from the human circulation. In the mosquito's stomach 

 these sperms fertilize the female cells, a single sperm uniting with each 

 (Fig. 29, B), and as many as five hundred of these fertilized egg cells- 

 have been found in the 

 stomach of a single mos- 

 quito. The fertilized egg- 

 cell becomes elongated and pointed at one 

 end (Fig. 29, C), and finally works its way 

 into the stomach-wall of the insect (Fig. 

 30), where the embryo-cells grow and, in 

 fifteen to twenty days, produce large cysts 

 (Fig. 32, C) each of which is filled with 

 thousands of new needle-shaped spores. 

 These cysts, which are on the outer wall of 

 the stomach (Fig. 31), ultimately burst and 

 the hosts of contained spores (Fig. 32, C, S) 

 are set free in the body cavity and, conse- 

 quently, in the blood of the mosquito. Some 



of them find their way into the salivary glands (Fig. 32, G) and then 

 into the salivary ducts, whence, at the insect's next Malarial infection 

 meal, they are again injected with the saliva into by the 



the blood' of another human individual. In this "Mosquito bite" 

 manner malarial infection is handed on from subject to subject. 



FIG. 28. NORMAL BLOOD COR- 

 PUSCLE AND MALE ( c ? ) AND 

 FEMALE ( 9 ) REPRODUCTIVE 

 FORMS OF THE MALARIAL 

 ORGANISM. 



Magnification 1600 diam- 

 eters, after Ruge. 



(i 



v^..^J- 



/ 



V s 



FIG. 29. THE REPRODUCTIVE FORMS OF THE MALARIAL ORGANISM IN THE 



MOSQUITO'S STOMACH. 



(Alter Schaudinn and R. Koch.) 



A. Female, or egg cell. A 2. Male cell giving off sperms. B. Fertiliza- 

 tion of the egg-cell. C. The fertilized egg-cell. Magnification 37o diameters. 



Three varieties of malaria are distinguished: "tertian," 

 where the fever and chills recur every forty-eight hours; 

 "quartan," where they are separated by an interval of sev- 

 enty-two hours, and, lastly and most dangerous of all. the irregular 



Forms of 

 Malaria 



