CONVICT LABOE FOE EOAD WOEK. - 107 



they need not be uncovered except for cleaning and filling. Wooden 

 covers are not satisfactor}^, as they do not fit tightly enough to keep 

 out mosquitoes and are hable to warp. Cesspools and privies must be 

 constructed in such manner as to prevent access of mosquitoes, while 

 tin cans, broken bottles, sagging gutters, holes in rocks, hollows in 

 trees, or any other places which may hold water and serve as breeding 

 places for mosquitoes, should not be allowed to remain about a camp. 

 Areas of stagnant water, when they can not be drained, should be 

 treated once every ten days with a half and half mixture of crude oil 

 and kerosene. 



Screens and mosquito bars are indispensable in keeping out mos- 

 quitoes wherever they are prevalent, and in some places both screens 

 and bars will be found necessary. At those camps in which steel con- 

 vict cages are in use screening is comparatively simple and inexpen- 

 sive, and satisfactory results are obtained by carefully screening the 

 fom* open sides. Experience has shown that mosquitoes can some- 

 times pass through a metal-wire screen containing 16 strands or 15 

 meshes to the inch, but can not pass through one which contains 20 

 strands or 19 meshes to the inch.^ Screens made of iron wire are 

 cheapest at first cost, but require painting in order to make them last 

 through a season. The paint reduces the size of the mesh, so that 

 ventilation is interfered with to a considerable extent. On the other 

 hand, screens of brass or copper last almost indefinitely and though 

 expensive at first may be cheapest in the end. 



Mosquito bars are well adapted for camp use and should be a part 

 of the regular equipment in regions where mosquitoes are numerous. 

 They may be suspended from the ceiling and tucked in around bmiks 

 or may be arranged so as to rest upon the floor all around the bed. 



VOLATILE OILS. 



Oil of citronella, oil of pennyroyal, and similar substances are used 

 frequently to rub on the face and hands and to place on the bed- 

 clothes at night, and have some effect in keeping away mosquitoes. 

 They evaporate rapidly, however, so that their benefits are only 

 temporary. None of them will last through the night. 



ISOLATION AND PROTECTION OF PERSONS SUFFERING WITH MALARIA. 



Any prisoner who is suffering with symptoms which may reason- 

 ably be ascribed to malaria should be isolated at once and carefully 

 protected from mosquitoes by mosquito bars. This will prevent 

 mosquitoes which are not infect(^d from biting the patient and so 

 becoming infected and capable of transmitting the disease to others. 

 Mosquito<^s can not transmit malaria without first bitiiig a person 



' Kosenau, " Preventative Medicine and Uygiene," p. 205. 



