MIRACLES OF SCIENCE 



gains admission at a port it is brought by rats that 

 have escaped from shipboard. Rats may transmit the 

 disease to allied animals. In this way, for example, 

 many of the ground squirrels have become infected 

 in California; and in one case at least a child acquired 

 the disease through being bitten by one these animals. 



Obviously, then, there is no ultimate safety except 

 through destruction of the rats. But in the mean 

 time much may be accomplished in the Canal Zone by 

 either raising the houses three feet from the ground 

 on supports of concrete or other material, covered 

 with tin, so that the rats cannot secure a footing on 

 them. If placed on the ground they must rest on a 

 floor of concrete. The buildings are submitted to in- 

 spection at regular intervals; those not in a sanitary 

 condition in the cities must be placed in that condition, 

 if possible, by the owner, or they are condemned and 

 destroyed. 



Furthermore direct war has been waged upon the 

 rat. Thus 17,000 of these animals were killed in Pana- 

 ma City in a single year. So rigid has been the in- 

 spection of ships, and so effective the warfare upon 

 the rats that the plague has gained no foothold. 



THE "TYPHOID FLY" AND ANTI-TYPHOID VACCINE 



The chief remaining diseases that formerly ravaged 

 the Canal Zone are typhoid fever and cholera. These 

 diseases also depend to a considerable extent for 

 transmission upon an insect host, the offender this, 

 time being the common housefly. War is waged upon 

 the fly, as upon the mosquito, chiefly by destroying its 

 breeding places. So effective have been these pre- 

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