7 6 
Parasitic Arthropods 
When a person is exposed to infestation, the trouble manifests 
itself after eight or ten days, though there usually elapses a period of 
twenty to thirty days be¬ 
fore there is a suspicion of 
anything serious. The first 
symptom is an intense 
itching which increases 
when the patient is in bed. 
When the point of irrita¬ 
tion is examined the gal¬ 
leries may usually be seen 
as characteristic sinuous 
lines, at first whitish in 
color but soon becoming 
blackish because of the con¬ 
tained eggs and excrement. 
The galleries, which may 
not be very distinct in 
some cases, may measure 
as much as four centi¬ 
meters in length. Little 
vesicles, of the size of a 
59. Scabies on the hand. After Duhring. . , . . , . 
pm head are produced by 
the secretions of the feeding mite; they are firm, and projecting, and 
contain a limpid fluid. Figures 58 
and 59 show the typical appearance 
of scabies on the hands, while figure 
60 shows a severe general infesta¬ 
tion. The intolerable itching induces 
scratching and through this various 
complications may arise. The lesions 
are not normally found on the face 
and scalp, and are rare on the back. 
Formerly, scabies was considered 
a very serious disease, for its cause 
and method of treatment were un¬ 
known, and potentially it may con¬ 
tinue indefinitely. Generation after 
generation of the mites may develop 
and finally their number become so After Morrow. 
