380 
Patliologiccd effects of Plithiriis 
EXPERIMENTAL OBSERVATIONS ON THE EFFECTS OF 
PHTHIRUS BITES. 
Tieche {loc. cit.) states that the first effect of the bite, observed under 
experimental conditions, is to produce a brown spot which turns bluish 
after eight hours. He saw maculae attain a diameter of 3 cm. in sus¬ 
ceptible persons and it took twelve days for them to disappear. 
Having found no other record of such experimental observations in 
the literature available, I can'ied out two experiments to which the 
following protocols relate: 
Exp. 1. An adult crab-louse, the sole survivor of about 200 insects 
taken from a soldier the previous evening, was placed on my arm on 
31. vii. 15. The louse was confined in a cell. It proceeded to feed at 
once, and after 25 hours, not having shifted its position, it was removed 
and the seat of the bite marked. The bite produced no itching, but a 
faint, deep-seated violet spot 2 mm. in diameter was visible, and it 
took a week in which to disappear. 
Exj). 2. Some FMhirus eggs, taken from a soldier, were allowed to 
hatch in a tube carried in the inguinal space next to the body. The 
freshly emerged larvae were placed on my laboratory assistant’s leg and 
confined in a stocking on 5. v. 17. The larvae shortly began to feed, 
remaining fixed to one hair. There was no itching or any effect observ¬ 
able for four days during which the larvae stayed in the same spot. 
On the fifth day, in the morning, the lice being still in the same position, 
the seat of the bite appeared faintly pink, and by the afternoon it had 
darkened slightly. The larvae then moulted and moved to another 
place, the seat of the first prolonged feed no longer being discernible after 
two days, although its position had been marked from the start. As the 
insects attained the adidt stage, the ejfects of further bites became more 
marked, typical maculae appearing in places where the bisects had anchored 
themselves for 12-24 hours at a tinie^. These spots disappeared in about 
a week. The bites at no stage produced any itchiness. 
MELANISM. 
Some authors state that the pigmentation due to Phthirus may be 
generalized, the discoloration amounting almost to blackness and in¬ 
volving the mucous membranes and nails. Thus Le Play and Dehu 
(1906, p. 141) describe such a case in a woman of 60 years, but they add 
1 Vide p. 72 where it is stated that P. h. capitis when maturing or adult produces more 
lasting effects than larvae. 
