Screening and Destruction 201 



sionally, when mosquitoes are very numerous on 

 hospital buildings, especially yellow fever wards, 

 it is desirable to double-guard the entrance by 

 providing a screened vestibule. Such a vestibule 

 should be at least six feet wide from door to door, 

 and should be arranged so that one door must be 

 closed before the other can be opened. A number 

 of devices will readily suggest themselves. One 

 that has been used with considerable success is 

 a pulley and rope arrangement. 



If screened doors are to be used, the frame should 

 be made of light material that will resist warping 

 and swelling, and should be provided with a brace 

 to prevent sagging. A good contrivance for this 

 piirpose is two rods connected by a turnbuckle. 

 One free end is fastened at the upper comer on the 

 hinge side of the door, and the other free end to 

 the comer diagonally opposite, as shown on the 

 diagram opposite. Tendency to sagging is cor- 

 rected by twisting the turnbuckle. 



The screen panels should be protected from 

 injury by hands and feet by fastening over the 

 gauze on the outside of it, so as not to interfere 

 with any mosquito catching that may be required, 

 one quarter inch or three eighths inch galvanized 

 wire netting made of wire sufficiently thick to 

 resist denting by a push of the hand or foot against 



