53 



le. Very beautiful preparations, with the corpuscles lying singly, 



s thus obtained. 



This little apparatus can readily be made at the blowpipe. 



Fig. 1. — Rosenau's spreader for making blood smears. 



THE PERIOD OP IUOUBATIOU OF" YELLOW FEVER 



The exact period of the incubation of yellow fever is a matter of 

 ;at importance in quarantine and public-health work. For years 

 > quarantine regulations of the Marine-Hospital Service required 

 letention of five days, which was considered amply safe to cover 

 i period of incubation of the disease. The regulations of the Pub- 

 Health and Marine-Hospital Service, promulgated August 10, 

 )3, lengthened the time of observation in special cases to six days, 

 sing this action upon the recent experimental work which has made 

 sossible to determine the period of incubation of yellow fever with 

 $at exactness. 



