32 AOTMAL PARASITES 



of care aiad importance. So also with the com- 

 mon flesh-fly, musca carnaria. They thus add 

 greatly to the misery of certain endemic diseases, 

 as the affections of the eye in Egypt. The house- 

 fly may also deposit its eggs, and its larv88 be 

 found in wounds, and the orifices of the body. 

 The eggs and larvae of the bot-flies may live on 

 the skin, and there form boils. In South Amer- 

 ica this parasite is reported as by no means rare 

 upon man. Von Humboldt called it oestrus hu- 

 manus. It is not yet, however, settled whether 

 this is different from the bot of the horse, sheep, 

 ox, stag, and other bot-flies. Fluctuation will be 

 sought for in vain in the tumors produced by 

 them, but an orifice will be found in the swelling, 

 from which a little moisture constantly oozes, and 

 through which the hinder part of the oestrus is 

 kept in communication with the air. The prog- 

 nosis is favorable, and immediate cure is only pos- 

 sible by incision, and the removal of the oesfrus. 



The Medina- worm, or Guinea hair-worm, _^Za- 

 ria medinencis, is an inhabitant of another por- 

 tion of the world, and need not, therefore, be dis- 

 cussed here. On the other hand, we must take 

 some notice of the sand-flea, pulex penetrans, since 



