BA C TERIA ' AND S ANITA TION 



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 

 ane they recognized? (Fig. 132.) 



They should be kept out of houses FIG. 132. CULEX OR COM- 

 .. 1111 MON MOSQUITO, above (pos- 



by screens or from the beds by sibly carries dengue fever)> 

 Kerosene should be 



netting. 



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- 



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.) 



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 



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). 



