G. H. F. Nuttall 
73 
centre of each papule was congested and it was surrounded by a small 
pink halo; each papule arose from a separate bite 1 . At ( C ) the whole area 
appeared fairly sharply defined, reddened, and dotted over with slightly 
darker nodular elevations, the skin feeling roughened and markedly 
thickened; it itched a good deal for several days. On stretching the 
skin a yellowish-brown discoloration was observable at the seat of each 
bite and over the whole area at ( C ). By 16. vii. 17, all traces of the 
bites at (A) had disappeared, at (B) there was still some discoloration 
and roughness. At ( C ) the incipient melanodermia gradually faded 
away but faint traces persisted until 28. vii. 17, it had lasted a month; 
slight thickening of the skin was still observable on 16. vm. 17. 
My Laboratory Assistant’s arm, which has been used as feeding 
ground for months, shows well-marked diffuse bronzing over the whole 
surface on which the lice have fed. It will doubtless take longer for 
the bronzing to disappear than, in my case. 
Hase (xi. 1915, pp. 153-163), who studied the effects of lice on 
behalf of the War Office in Germany, reports upon some suggestive 
observations he made. He states that he questioned 1,000 persons on 
the subject, and that he was able to place them under four groups: 
(1) persons who are not attacked by lice, (2) who are attacked con¬ 
tinuously and are sensitive to bites, (3) who, after suffering much from 
bites become immune to their effects, and (4) those who have been 
bitten continuously but do not suffer from the effects. Groups (3) 
and (4) he regards as dangerous “carriers,” since they do not complain. 
The prevalence of lice among Russian civilians, and the marked toler¬ 
ance shown by them to louse-infestation, is regarded by Hase as doubt¬ 
less due to a process of immunization commencing in childhood. The 
author gives no figures as to the relative numbers of persons in each of 
the groups he distinguished. He mentions the cases of (1) a man who 
remained untouched by lice but who suffered from fleas, (2) a man who 
suffered from the effects of lice and fleas, and (3) a man who was bitten 
by lice but avoided by fleas. 
That a tolerance to the presence of lice upon the person can be 
acquired in a relatively short time by some individuals, is evident from 
what a number of soldiers have told me. They have stated that after 
having been tormented for about a couple of months they no longer 
experienced any particular discomfort from the insects they har¬ 
boured. 
1 The adults were removed as they emerged, therefore there were fewer bites inflicted 
toward the end of the experiment. 
