550 Veterinary Medicine. 



by rows of teeth turned backward, which when, imbedded in the 

 skin, hold so firmly that the parasite may be pulled in two in any 

 attempt to pull it out. Above this dart and on the two sides lie 

 the cheliferse (horns), each furnished with three or four teeth 

 turned outwardly and more or less recurved, by which the dart is 

 worked into the skin. Finally, on the lateral sides of this cen- 

 tral apparatus, are the two maxillary palpi, which are not inserted 

 into the skin, but applied against it and operate as feelers prior to 

 and during the insertion of the dart and cheliferse. The maxil- 

 lary palpi are club shaped and soft. 



Ticks pass through three moultings before they attain to the 

 sexually mature eight-legged form, and though the hexapod 

 larvse attach themselves to animals and irritate the skin by their 

 bites, it is only the mature, impregnated egg-bearing female that 

 lives exclusively on blood and sucks this to excess. 



While given species of ticks show a preference for particular 

 genera of animals, yet ticks generally in their vagabond life will 

 leave the long grass and brush where they have been hatched to^ 

 become temporarily the guests of any passing animal. It is, 

 therefore, premature to seek to identify any single species of tick 

 as the only bearer of the infection, and it is quite possible that 

 any one of several species may contribute to its propagation. 



Experimental Infection by the Tick. W. Williams muzzled 

 four sheep from a healthy district and turned them for several 

 hours a daj' on a tick-infested field, and two sickened — one on the 

 eighth day and one on the sixteenth. Twelve ticks sent out of 

 the district and put on a healthy sheep caused illness on the tenth 

 day. In a second experiment with ten sheep, during a colder 

 spring, when there were fewer ticks, no deaths occurred. 



Meek and Greig-Smith turned twenty sheep on a tick-infested 

 louping-ill pasture, six of the number wearing muzzles to prevent 

 grazing, seven having been dressed with a mixture of sweet oil, 

 2 quarts ; castor oil, i quart ; train oil, i quart ; pitch oil, 3 gills, 

 and cade oil, i gill, while the remaining seven were unmuzzled 

 and undressed. The muzzled sheep were regularly taken out 

 and fed on food from a healthy locality. At the end of a fort- 

 night oils were reapplied on the second lot (seven sheep). No- 

 ticks appeared on these sheep, while many were found on the 

 undressed ones. On the fifteenth one of the unmuzzled and un- 



