A BACILLARY INFECTION OF THE COPULATORY 
APPARATUS OF PEDICULUS HU MAN US. 
By J. A. ARKWRIGHT and A. BACOT. 
(From the Lister Institute of Preventive Medicine.) 
In the paper on the association of Rickettsia with Trench Fever, by Arkwright, 
Bacot and Duncan (1919) mention is made of a bacillary infection of the 
excreta and guts of lice (Pediculus humanus). A Gram-negative cocco-bacillus 
was isolated in pure culture. It was non-motile, fermented glucose, mannite 
and lactose very slowly, and formed acid and clot in milk in about 14 days. 
It was not pathogenic for guinea-pigs. When plated from pure culture, 
rough and smooth colonies were formed similar to those which are known to 
occur in bacilli of the B. coli group. 
Continuation of our work with Pediculus humanus has placed us in posses¬ 
sion of further information concerning the relation of this bacillus to its host. 
Sections of lice from a stock which has been inbred for nearly five years 
show a high percentage infested with this parasite. It is probable that crowding- 
together in boxes for so long a period has caused these lice to be more uniformly 
infected than wild ones. In male lice the cocco-bacilli are seen in the folds 
of the vesica yenis, whereas in females they occur in the vaginal orifice and 
passage leading to the ovaries 1 . No evidence that the gut is involved has been 
obtained from the very numerous sections examined. 
Preliminary culture experiments with the guts of 24 lice taken at random 
from the stock were carried out. The insects were washed in 2 per cent, lysol 
followed by rinsing in sterile salt solution and the alimentary tract was dis¬ 
sected out on flamed slides with sterilised needles. Each specimen was trans¬ 
ferred by means of a platinum loop to a separate nutrient agar tube and placed 
at the lower part of the slope. 
Half the tubes were placed under anaerobic conditions, six at 35° C., and 
six at 26-5° C.; the remaining twelve were incubated aerobically at similar 
temperatures. Growth took place in seven of the twelve kept at the lower 
temperature, including both aerobic and anaerobic tubes. Subsequently five 
of the remaining tubes, which had been transferred to the cooler incubator, 
also produced growths. All the cultures appeared similar both to the naked 
eye and on microscopic examination. Subcultures were plated from the tubes 
and found to be pure. Both subcultures and plates were made with ordinary 
1 See Nuttall (1917), Parasitology, ix. 293 for description of copulatory apparatus of (Jand$. 
