18 ANIMAL PARASITES 



skin becomes quite red, aud, as with the other 

 forms of pediculi, exhibits the scabs described — 

 papules, vesicles, and pustules. When the insects 

 have preyed upon the individual for a long time, 

 the continued irritation causes continued conges- 

 tion and infiltration, increasing the deposit of pig- 

 ment in the skin, which finally becomes rougher, 

 darker, and thicker than natural — sometimes ab- 

 solutely as black as the negro's. 



The presence of these vermin, as with the other 

 kiuds, cause, from the scratching, artificial ecze- 

 matous eruptions, and in general call forth, on the 

 cutaneous surface, any disease of this tissue to 

 which the individual so afiected is liable, or pre- 

 disposed to. The enormous numbers of these 

 vermin which have at times been seen, and their 

 apparently rapid production, has given rise to the 

 idea that they were also generated spontaneously. 

 But this, as we said above, is owing to incorrect 

 observation and erroneous deduction. The jjed- 

 iculi vestimenti^ like the other pediculi, thrive best 

 when let alone, and where morbid cutaneous se- 

 cretions attract them. They may be always 

 detected on the clothing, if not on the body. The 



