484 
Combating Lousiness 
of 8000 men within 4 days by this method, and used it for a period of 
7 months. At the end of his communication he states incidentally that 
the temperature inside the room attained 100° C. In short the heat pro¬ 
duced more than sufficed to kill the vermin, a fact which did not 
apparently occur to Eckert. 
2. PEDICULICIDES AND REMEDIES FOR LICE. 
General considerations. 
The mode of action of Pediculicides. 
Before considering the various remedies that are employed against 
lice, it is expedient to dwell briefly upon their mode of action, because 
it is evident that this must vary according to the nature of the remedy. 
Physical effects alone doubtless explain the pediculicidal action of 
indifferent fluids, oils and fats, since these will occlude the spiracles in 
the active stages and the opercular orifices of the nits, thus checking 
the insect’s respiratory processes (v. infra). Unless plentifully applied, 
the lethal action of such substances will necessarily be but partial and 
it is therefore usual to employ them as vehicles for insecticides. 
Mercurial ointment may be taken as the type of a remedy which exerts 
a combined effect, physical through the fat and chemical through the 
mercury which is stated to exert its insecticidal action through being 
volatilized. The speed with which an insecticide acts depends upon its 
penetrating power through the chitin and the external orifices in the 
insect’s exoskeleton coupled with its particular chemical affinity for the 
animal’s tissues. 
Direct toxic effects are induced by various mineral or organic vapours, 
operating either in solutions in which the insects are immersed or per¬ 
vading the atmosphere in which they are confined. These vapours act 
most rapidly when concentrated and when the temperature is moder¬ 
ately high as experiments have shown. Labbe and Wahl (1915, pp. 
872-888), who have made an experimental study of the effects of 
toxic vapours on lice, have reached conclusions similar to mine. They 
distinguish two stages of intoxication wherein the insect exhibits: 
(1) agitation, torpidity, spasms, etc. followed by (2) apparent death from 
which they may recover, and, if the exposure continues, (3) death. 
Insecticides act in various ways, relatively speaking, some immobilize 
quickly and have slow killing power, others immobilize slightly but 
kill more quickly, whilst others again are intermediate in their effects. 
