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PARASITES FREE DURING THEIR WHOLE LIFE. 183 



Most mammals have their peculiar species of acari, 

 and the horse has two which give rise to- different* skin 

 affections. Since the presence of these animals con- 

 stitutes the disorder, it may be easily caught ; man may 

 communicate it to domestic animals, and they may give 

 it to him. The itch-insect of man bears the name of 

 Sarcoptes scabici, and no other species than those of 

 Sarcoptes can be transferred from animals to man. 

 These animalcules have at different times been dili- 

 gently studied by many naturalists, and Dr. Fiiestenberg 

 has lately published a folio volume, under the title of 

 " Die Kratzmilben der Menschen und Thiere," with large 

 lithographic plates, and illustrations in the text. It is 

 possible that the pustular disease which prevails at Sierra 

 Leone is originated by some peculiar acarus. Another 

 acarus parasitical on man, the Persian Argas, is fortu- 

 nately unlmown in Europe. It is said to be common at 

 Mioiia, and prefers to attack strangers. Its stings pro- 

 duce acute pain, and travellers assure us that they may 

 be the cause of death. This acarus remains but a short 

 time on the person, and generally makes its appearance 

 during the night. It is called also the Miona bug. 

 Fischer of Waldheim has published a very interesting 

 memoir on this parasite. Justin Goudot has also ob- 

 served another Argas {A, Chinche) which torments man 

 in the temperate regions of Columbia. 



These Ai'achnida, for they are articulata with four 

 pairs of legs, often make their appearance where we 

 should not expect to find a living organism, and natural- 

 ists, under these circumstances, have, with the best faith 

 possible, supposed that they had seen these mites pro- 

 duced spontaneously without parents. We have seen a 



