536 
Combating Lousiness 
reappeared on 3 prisoners only; moreover, whilst 40-50 fleas were 
present per bed before treatment none were found subsequently. 
(There is no proof in either of these cases that naphthaline sachets 
were beneficial; the favourable result may have been due solely to 
the thorough disinfestation previously practised.) 
Busson states that naphthaline (quantity used and how applied 
not mentioned) did not protect him and a nurse against infestation. 
An isolated and imperfect observation. 
Expt 70: some lice survived 10 hrs contact with a cloth im¬ 
pregnated therewith (temperature?, not tested on man). Expt 91: 
lice killed in 3 hrs by contact with impregnated cloth worn near 
man’s body. Expts 171-177: the vapour, acting in vitro, killed all 
lice in 30 minutes at 33° C., but at 16° C. they were merely im¬ 
mobilized; others survived 3 hrs (? temperature). Expts 263-265: 
the vapour acting near man’s body, most of the lice survived 
10-20 hrs exposure. Expt 279: the vapour from sachets worn by 
verminous men, killed lice (all?) but the naphthaline had to be 
renewed every 3 days to be effective. Expt 300: crude naphthaline 
impregnating cloth worn near man’s body killed || lice placed in 
contact with it immediately after it was impregnated, but cloth 
impregnated 20-22 hrs previous to placing the lice upon it only 
killed t 4 ? lice in 4-5 hrs. Whereas the vapour of pure naphthaline, 
emanating from the substance placed in close proximity to the 
insects and carried near man’s body, killed lice in 4-5 hrs 
(Expt 311), crude unwhizzed naphthaline in the same period killed 
(Expt 312: contact took place here for the crude oily substance 
spreads in fabrics), and similarly, finely powdered commercial 
naphthaline in Expts 315-316 killed Lvs and of the lice 
respectively. 
Comments. These experiments demonstrate (1) that naphthaline 
is much more powerfully insecticidal either by contact or vapour 
at the temperature that prevails in clothing than at lower tempera¬ 
tures; (2) that its range of action is very limited, the insects only 
being killed when exposed to concentrated vapour or to actual 
contact with the substance; (3) that owing to evaporation naph¬ 
thaline must be renewed at intervals of about 3 days; (4) that crude 
naphthaline acts more powerfully than the pure substance, owing 
to its oily character which causes it to be imbibed by fabrics; 
(5) the impurities in crude naphthaline are in a measure insecticidal 
and they retard the evaporation of naphthaline with which they 
