A. Bacot and (x. Talbot 
233 
XII. EXPERIMENTS CONCERNING THE DEGREE OF ATTRACTION 
EXHIBITED BY DIFFERENT INDIVIDUALS FOR MOSQUITOES. 
It is a matter of general comment that some individuals are more prone 
to mosquito attacks than others. Finlay (1912) records that natives of Africa 
are least liable to attack and that people of northern races recently arrived 
in the tropics are most persecuted; he considered it probable that this 
preference depended upon the thickness of the skin, and the condition of the 
capillary circulation of the skin. In regard to the Yellow Fever mosquito 
(the species used in these experiments) Goeldi (1912) considered that the 
presence of perspiration attracted both sexes. The French investigators, 
Marchoux, Salimbeni and Simond (1912), concluded from experiments that, 
although Stegomyia fasciata readily bites both negro and red skinned races, it 
shows a preference for white skinned people. They further showed that this 
mosquito exhibited preferences among whites for young and vigorous persons, 
over aged, and anaemic ones. It is also very generally asserted that in the 
tropics seasoned whites enjoy a certain amount of immunity at the expense 
of fresh arrivals. 
As this factor of preference on the part of the mosquitoes for one of the 
experimenters was apparently influencing our results (see pp. 234-5), we 
planned a series of experiments in order to ascertain if possible some measure 
of its importance, and carried them out as opportunity permitted. The method 
adopted was similar to that already described in regard to the testing of 
culicifuges (see Section VII), but for the purpose of these trials two persons 
exposed their untreated arms simultaneously in the same cage for 10 
minutes. 
The following data relating to the persons who exposed their arms in the 
cages may be of interest. 
A. B. Age 51. Has never resided out of England until three years ago when he spent 
13 months in W. Africa. During and since that period has regularly allowed mosquitoes 
to feed upon his arms. Shows very slight reaction to bites. 
G. T. Age 35. Save for two months’ residence in N. France, has always lived in England. 
Has allowed mosquitoes to bite him frequently during the past four months, and showed a 
marked reaction to their bites, but seems to have gained some measure of immunity since 
the commencement of this research. 
H. Age 38. Born in Australia and lived for many years in Queensland; has resided in 
England for the past six years. Shows very slight reaction to bites. 
I. Age 48. Fourteen years ago resident off and on in Tropical South America for about 
ten years. Has since been resident in England. Shows marked reaction to bites. 
J. Age 18. Has never resided out of England. Shows a marked reaction to bites. 
K. Age 27. Has never resided out of England. Shows a marked reaction to bites. 
L. Age 54. About a year ago resided for 13 months either in Greece or Malta. Has 
never lived in the tropics. Shows slight reaction to bites. 
M. Age 31. Never resident out of England. Shows a marked reaction to bites. 
