DRUGS THAT KILL PARASITES. ANTIPARASITICS 



1. EXTERNAL ANTIPARASITICS. ANTEPIZOA 



Synon3^s: Antiscabious. antipsorics, antipediculous, antiphthiriacs; 

 mange remedies. 



Parasites of the Skin. — The numerous epizoa infesting the 

 skin of the domesticated animals which are to be combated with 

 antiparasitic remedies may be divided into two groups: animal and 

 vegetable. The animal parasites include the mange mites, of 

 which there are four species: sarcoptes, dermatocoptes, dermato- 

 phagus and dermatoryctes; the acarus mites [demodex follicu- 

 lorum], fleas, lice, hair and feather insects [mallophagse], ticks, 

 forest flies, bird mites, harvest mites, CEstrus larvffi, gad flies, 

 flies and gnats; also the different bird mites: feather-follicle 

 mites, feather-quill mites, feather mites, pigeon mites, etc. Of 

 the vegetable skin parasites, the most important are trichophyton 

 tonsurans (herpes) and achorion Schbnleinii (favus). 



Action of the Antiparasitics. — The antiparasitic medicines 

 operate upon the skin parasites by different processes. Some 

 apparently act like the specific nerve poisons, stunning and para- 

 lyzing the parasites. To this group belong the ethereal oils, nico- 

 tine, veratrin, carbolic acid, creolin and other aromatic substances 

 of the benzol series, and hydrogen sulphide. Other antiparasitics 

 act like the caustics, particularly the mercurial and arsenical 

 preparations. If, for example, a louse is removed from the skin 

 after the application of mercurial ointment and examined under 

 the microscope, there is observed a corrosive inflammation of the 

 digestive tract which is manifested by a bloody, profuse diarrhoea. 

 The alkalies, soda lye, potash lye, caustic lime and soap, dissolve 

 the external chitinous layer of the mange mites. Finally, some 

 agents operate in a mechanical way by closing the air canals, as 

 occurs, for instance, in the use of fatty oils on ticks. 



Classification. — The external antiparasitics may be divided 

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