BACTERIA AND SANITATION 



161 



animal, see "Animal Biology," p. 7). Afterwards a spore 



(in another stage) may be transmitted by this mosquito 



when it bites another person. The 



germ enters a red corpuscle, grows, 



and finally divides into many little 



spores. At this moment the cor- 

 puscle itself breaks up, setting 



free in the blood the spores and 



toxin formed. This causes the 



chill and fever. This develop- 

 ment usually takes forty-eight 



hours, hence the fever occurs 



every other day. These mos- 

 quitoes begin to fly at dusk. How 



are they recognized? (Fig. 132.) 



They should be kept out of houses FK;. 132. 



by screens or from the beds by 



netting. Kerosene should be 



poured on breeding places at the 



rate of one ounce for fifteen square 



feet of standing water. This 



should be repeated twice a month. 

 Cactus macer- 

 ated in water 



may be used, and forms a permanent 

 film on the water. Stagnant pools 



may be filled or drained (Exp. 4). 

 FIG. 133. PROTECTIVE . , , , , , 



WHITE CORPUSCLE Malarial patients should themselves be 



(phagocyte) digesting screened, as the chief 'source of danger to 



a microbe. 



others ; for only mosquitoes who suck 

 the blood of malarial patients will transmit the disease. 

 Even then it is only transmitted to those whose white 

 blood corpuscles are unable to protect them (Fig. 133). 



CULEX OR COM- 

 MON MOSQUITO, above (pos- 

 sibly carries dengue fever). 

 ANOPHELES OR MALARIAL 

 MOSQUITO, below (not always 

 infected). Body of malarial 

 mosquito is never held paral- 

 lel to the supporting surface 

 (unless a leg is missing) ; it 

 has five long appendages to 

 the head, the culex (above) 

 has only three. (Draw.) 



