76 



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 

 blackishbecauseof 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 

 pin head are produced by 



the secretions of the feeding mite ; they are firm, and projecting, and 



contain a limpid fluid. Figures 58 



and S9 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 xm- 



known, and potentially it may con- 

 tinue indefinitely. Generation after 



generation of the mites may develop 



and finally their number become so ^°- ^StS MOTrow^'"™ °' ^'^'''"- 



59. Scabies on the hand. After Duliring. 



