26 
Pediculus humanus 
nutrient agar and were kept aerobically at 35° C. Later attempts to cultivate 
direct from the dissected guts at 35° C. have proved successful, so that the 
failures at this temperature in the first trial must be attributed to some chance 
circumstance. It may be noted here that to dissect out the alimentary system 
of the louse without contaminating it with organisms infesting the copulatory 
apparatus would be very difficult if not impossible, as the pressure of the 
dissecting needles would tend to release the valves which close the openings 
to both the male and female organs. The later series of trials was therefore 
planned in order to decide whether the gut was infected or not. 
Six males, six females, and a like number of nymphs (in which the copula¬ 
tory apparatus is not yet developed), were taken from the stock and treated 
in the same manner as in the previous experiment except that the two 
terminal segments were left adhering to the gut. 
This experiment resulted as follows: six of the tubes containing the female 
and five of those containing the male guts produced growths of similar 
appearance to those in the previous experiment. Microscopically, when 
stained by Gram’s method, they all showed similar cocco-bacilli, apparently 
in pure culture. Subcultures on plates from two tubes selected at random 
from among the eleven infected supported this assumption. As regards 
the tubes containing the dissections of the guts of nymphs only one showed 
a growth, and this was obviously contaminated as the growth started apart 
from the introduced gut, was of an entirely different appearance and was 
composed of Gram-positive bacteria. 
Cultivation therefore strongly supports the microscopic evidence obtained 
from sections. We conclude that this bacterium may be correctly termed 
a parasite of the copulatory apparatus of Pediculus humanus and we propose 
for it the name of Bacillus pediculi. 
REFERENCE. 
Arkwright, Bacot and Duncan (15. iv. 1919). The Association of Rickettsia with Trench 
Fever. Journ. of Hygiene, xvni. 76-94. 
