as affecting Domesticated Animals. 



41 





ticks adhering; to the head and face of a horse sent to the College 

 for examination as to soundness. The animal had been forwarded 

 from the country to a gentleman in town a few days before, and 

 the parasites had not been detected until seen by ourselves, 

 probably in consequence of their small size and brown hue, 

 which pretty nearly approached the colour of the horse. We 

 were enabled to obtain many specimens with their rostrum 

 — sucking proboscis — entire, always a difiicuit thing to effect, in 

 consequence of the peculiarity of its formation, and its firm 

 insertion in the skin. 



We here insert an illustration of one of these ticks, drawn on 

 an enlarged scale from a 

 specimen still in our pos- 

 session. (See Fig. 2.) 



The chief points of in- 

 terest in the structure of the 

 tick are well represented in 

 the preceding illustration. 

 The barbed or serrated 

 rostrum, by means of -p^ |^ 

 which, as the barbs point 

 backwards, the parasite is 

 enabled, almost without 

 muscular effort, to retain its 

 hold of the skin, is clearly 

 depicted. The externally 

 barbed rostrum is found to 

 sheath the mandibles, two 

 in number. These are three-jointed, " the basal joint being inter- 

 nal, the second external and long, and the third short and denticu- 

 late." * The palpi, situated close to the rostrum, one on either side, 

 are broad and large, and in some specimens would seem from their 

 near approximation to the rostrum to be capable of emljracing it. 

 The abdomen, or body of the parasite, is formed of an exceed- 

 ingly extensile membrane, whereby the creature is enabled to 

 receive, without inconvenience, a large quantity of blood into 

 its digestive system to be husbanded for its future wants. The 

 legs are eight in number, and are attached to the under part of 

 the body at its anterior half, having their places of attachment 

 very near each other. They are of nearlv equal size and length, 

 and are furnished with seven joints. At their free extremities 

 they are tipped Avith two recurved hooks, having a fan-like 

 expansion of membrane between them. On the back of the 

 creature, immediately behind the palpi, a cuticular shield-like 



Ixodes Riciiuis. JLiirnified. 



* ' Micrographic Dictionary,' Article Ixodes. 



