556 SPORADIC DISEASES. 



covers of the tick, as will be shown hereafter — louping-ill has 

 been entirely eradicated. 



The tick is a true blood-sucking parasite, belonging to the 

 family Ixodidm, the class Arachnidcv, and order Acarince. The 

 mouth of the tick is provided with a serrated beak or rostrum, 

 which enables it to pierce the skin, and retain its hold very 

 firmly, and almost without effort, as the barbs or serrations 

 point backwards. 



The species are very numerous, V)ut the best known are the 

 Ixodes ricinus, dog-tick, the Ixodes reduvius and Ixodes plumhcns, 

 sheep and cattle tick. Those found during the investigation 

 were recognised liy Mr. Moore, British Museum, as Ixodes 

 ricinus, erinaceus, and marginatus. 



During this investigation we found ticks upon every variety 

 of soil, and at different altitudes — close to the sea level in 

 Skye, and at a height of 2000 feet in the inland districts ; in 

 fact they will be found as high as sheep will go, provided 

 always old grasses are abundant to afford cover, as they are thus 

 protected from injury, and are left at comparative rest during 

 the periods they are not obtaining Idood from the animals which 

 they attack. Prompted by hunger, they quit their hiding- 

 places, and attack any animal that may come in their way, 

 by plunging their beaks or sucking proboscides deeply into the 

 skin, particularly about the face, root of ears, lower parts of 

 breast, between the thighs, in fact into those parts of the skin 

 covered more with fine hair than wool. 



Thus fixed, they will hang for days together sucking the 

 blood, until their bodies become distended to eight or ten times 

 their original size ; tliey then quit their hold, fall to the ground, 

 and lay their ova, which remain dormant until next spring, and, 

 shortly after they are hatched, they most probably attack the 

 sheep, and after they once bite remain firmly fixed in the skin. 



It was a noticeable fact that when dead or dying sheep were 

 examined the ticks were found already dead, or in a dying con- 

 dition, in almost every instance of louping-ill. 



Eabbits, ferrets, stoats, weasels, and more rarely hares, are 

 attacked by ticks, but there are no instances recorded of these 

 animals becoming infected by louping-ill. This is probably 

 due to these hosts proving unsuitable habitats for the develop- 

 ment of the organism inducing " louping-ill," but horses are 



