THE PATHOLOGICAL EFFECTS OF 
PHTH I BUS PUBIS. 
By GEOEGE H. F. NUTTALL, F.R.S. 
{From the Quick Laboratory, University of Cambridge.) 
CONTENTS. 
PAGE 
Introduction .. ... 375 
General effects of parasitism with Phthirus ..... 375 
Maculae caeruleae.377 
Experimental observations upon the effects of Phthirus bites . . 380 
Melanism ............ 380 
Summary and Conclusions . . . . . . .381 
Compared to Pediculus humanus, the part played by Phthirus pubis 
in pathology is inconsiderable because: (1) it is not known to convey 
any infective disease, (2) it is not so prevalent, and (3) it on the whole 
produces slight effects, for man may be infested more frequently without 
knowing it. 
Imhof is cited by Brumpt (1910, p. 550) as believing that the crab- 
louse may convey tuberculosis, but loose statements of this kind abound 
in medical literature and bear no weight. On the other hand, secondary 
skin infections may arise owing to self-inflicted scratches by infested 
persons in response to the itching that the parasites may cause. 
That the insect is less frequently encountered on man than P. 
humanus {capitis and corporis), is exemplified by Greenough’s Boston 
statistics (already quoted, see p. 84) wherein out of 864 verminous 
persons admitted to hospital, only 27 (roundly 3 %) were found infested 
with Phthirus. 
GENERAL EFFECTS OF PARASITISM. 
Although Pinkus (1915, p. 239) states that crab-lice are not especially 
important in this war, I have had ocular evidence to the contrary in 
a limited way, given an instance in which a considerable number of 
soldiers in barracks became infested by these parasites which caused 
some of the men many sleepless nights. 
Pruritus is the first symptom that draws attention to the presence of 
crab-lice; it can be violent and lead to much scratching day and night. 
Parasitology x 
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