432 
Combating Lousiness 
result can be obtained by more moderate means. In accordance with 
my experimental results I have long urged on those who had to do with 
practical disinfestation to employ lower temperatures (55-70° C.) for 
killing lice. This was urged not only in the interests of economy in fuel 
and time but also to save clothing from the deleterious effects of needless 
superheating. Experiments under practical conditions were carried out 
at my suggestion by Captain Harold Orr, Canadian A.M.C., and later 
continued by Captain J. T. Grant, R.A.M.C., and Lieut. A. D. Peacock, 
R.A.M.C., and these amply confirm my experimental results which were 
communicated to Captain Orr three years ago. 
Grant and Peacock’s experiments (MS. Report, W.O. i. 1918) were 
carried out in hot-air disinfestation huts (see p. 441) containing blankets 
or clothing together with living test-lice and nits supplied by Mr A. 
Bacot, Entomologist to the War Office. Active lice to the number of 
15-20, and 50-100 nits, were used for each test, the insects being 
contained in gauze-covered pill boxes or attached to cloth. Maximum 
thermometers were used for recording the temperature, and the exposure 
time was reckoned from the moment that the desired maximum tempera¬ 
ture was attained in the hut. The test-insects were distributed in various 
parts of the hut in the pockets of clothing, etc. After the lice had been 
exposed, they were kept under observation by Bacot to determine if any 
had survived. I extract the following essential data from the lengthy 
experimental protocols. 
Orr’s preliminary tests, made with lice and nits placed with clothing in various 
parts of the hut, had proved that exposure at 54° C. or at 60° C. for 15' was lethal. 
Result (-{- = killed, or 
Maxim, temperature 
to which lice and nits 
were exposed ° C. 
Duration of 
exposure in 
minutes 
0 = not killed) 
Active stages 
Nits 
Remarks 
O 
00 
60' 
O 
O 
51-5° 
15' 
+ 
O 
53° 
15' 
+ 
O 
lice soft 
55° 
30' 
+ 
+ 
3 tests, lice soft 
56° 
20' 
— 
+ 
57° 
30' 
+ 
+ 
67° 
15' 
+ 
+ 
lice soft, nits shrivelled 
These results do not give the minimum time required to kill nits and 
lice like those I have tabulated on pp. 429, 430, but they show what can 
be done under practical working conditions. Lice exposed to 48° C. and 
below survived; all lice and nits exposed to 55°C. or over were killed; 
51-53° C. killed the active stages but not the nits. Therefore to allow a 
