196 THE INVISIBLE WORLD 



this way, and in this way only, is the fever com- 

 municated from one person to another. Only in 

 this way does the fever become epidemic. 



As soon as one is infected, the germs multiply 

 in great numbers, and generate the yellow fever 

 poison. This poison sickens the patient, causes 

 headache, chills, fever, nausea. 



In a day or two there is a change. If for the 

 better, the patient recovers. If not, there is a re- 

 lapse. All the symptoms return with intensified 

 severity. The skin turns yellow. There is black 

 vomit. The patient dies. 



The disease is extremely fatal. Out of every 

 hundred cases about seventy die. In the warm 

 countries of the South the mortality is large every 

 year. 



Fortunately, a serum has already been dis- 

 covered which promises to become a true antitoxine. 

 Timely and properly administered, it will, no 

 doubt, greatly reduce the mortality and make this 

 dreadful fever more endurable. 



The true way, however, to treat this disease, is 

 to prevent it. Lock the door before the horse is 

 stolen. The habits of the murderous mosquito are 

 nocturnal. It does its mischief by night. Screen 

 against it. Keep the intruder at a distance. 

 Especially screen every one sick with the fever. 

 Prevent the mosquito from spreading the disease 

 by carrying germs from the sick to the well. 



Screen by night, and spray with kerosene by day. 

 Spray all the breeding places of the mosquito. 



