28 
the remaining 911 specimens, serving as a malaria indicator for the 
spring season, 3 mosquitoes between May 15 and May 26, were 
definitely shown to contain oocysts, indistinguishable from those 
seen in mosquitoes experimentally infected with human malaria. 
In the investigation of man as the responsible winter carrier, 1,184 
persons, residing on the plantations selected, were examined for 
malaria parasites. Four hundred and ninety-two infections were 
identified microscopically; 317 cases were of the subtertian type, 8 
were mixed infections, and the remainder were of the simple tertian 
type, with the exception of one quartan case. 
In the consideration of these infections an important fact stands 
out: nearly one-fourth (2J/-.8 per cent) of the human carriers harbored 
gametocytes. 
It was proved that from a group of 103 persons, examined in 
March, 1915, 8 of the 15 gametocyte carriers identified, were simi¬ 
larly infected during the preceding fall. 
The incrimination of man as the sole winter carrier is emphasized 
by the fact that 3 malaria-infected Anopheles quadrimaculatus were 
found in the homes of these gametocyte carriers during May 15 to 
May 26, previous to which time 1,180 specimens of Anopheles from 
this source were found to be negative. 
ACKNOWLEDGMENT. 
The writer wishes to acknowledge his appreciation to the various 
officials of the Mississippi Delta Planting Co. for the material assis¬ 
tance rendered in the collection of data for this study. Through the 
kindly services of the general manager, Prof. Fox, and his assistant, 
Mr. Young, the cooperation of the plantation managers was obtained 
in securing blood specimens. The temperature chart and the sketch 
map of the plantations were obtained through the assistance of these 
gentlemen. Acknowledgment is likewise made to Dr. Miller and Dr. 
Lane, of the medical staff, for their intelligent cooperation at all 
times. Thanks are due the chief medical officer, Dr. Miller, for pro¬ 
viding generous laboratory facilities and offering personal assistance 
in collecting mosquitoes and in securing blood specimens. 
