64 THE FOUNDATIONS OF SCIENCE 



of their insect host. By means of the bite of an 

 infected insect, the disease was recommunicated to a 

 human host, and a new cycle of existence was entered 

 upon. 



Only one particular type of the mosquito or gnat 

 family, to which the name Anopheles has been given, 

 seems to serve in the distribution of malaria fever, 

 and among them the females are the bloodsuckers. 

 Species of this insect are found in almost every part 

 of the world, including England, and it is from the 

 study of their habits of life that malarial fever has 

 been swept away from many of its old haunts. These 

 gnats breed in stagnant water, and seldom fly about 

 except between sunset and sunrise. The breeding- 

 places can be destroyed by some system of drainage, 

 or by the filling in of places where pools of water are 

 apt to collect. Again, a thin layer of petroleum 

 oil over a sheet of water which cannot be drained, 

 will prevent the development of the larva. Wire 

 gauze screens to windows and doors and mosquito- 

 nets round beds will protect the inhabitants during 

 the period of the night, when these creatures are 

 active. 



Malarial fever or ague was once well known in the 

 fen districts of England, but it was stamped out, 

 probably by the progressive drainage, and the suc- 

 cessful treatment of the occasional sufferer by quinine, 

 before the true cause of the disease had been ascer- 

 tained The mosquito which conveyed the infection 



