216 SHEEP: BREEDS AND MANAGEMENT. 



How hydatids gain access to the body of the sheep has 

 been clearly established both by experiment and observation. 

 Hounds, shepherd and other dogs roaming over pastures and 

 root fields commonly leave behind them matured segments of 

 tapeworms in their excrement. Each of these little flat white 

 fragments, with which all dog owners are familiar, is loaded 

 with eggs, which soon escape on to the ground, and having 

 become free are swallowed with the food of the sheep, or 

 failing to be thus safeguarded perish and decompose. Safely 

 landed in the intestinal canal the period of incubation com- 

 mences, and soon each egg discharges a minute embryo, 

 which, by some means as yet unexplained, finds its way to 

 the brain, there to develop into a bladder-worm or gid 

 parasite. In order that this creature may become a tape- 

 worm, it must, as we have remarked, pass back into the dog. 

 Many, no doubt, fail to return to their canine host, as many 

 tapeworm eggs fail to reach the sheep. Some perish in the 

 brain of the lamb, and degenerate into a pasty mass, in which 

 case the host triumphs over the guest, but more frequently 

 the sheep succumbs to the destructive influence of the 

 parasite. It is then that further development of the latter 

 is rendered possible, for the dead sheep may become food 

 for the dog, and should the head with its living contents be 

 eaten, then development of the hydatid brood into tapeworms 

 is assured, and the life cycle of the parasite rendered com- 

 plete. If, however, the head of the infested sheep be not 

 consumed by dog or fox, or some other suitable creature, then 

 the bladder-worm perishes, and decomposes with the brain 

 which contains it. This is, no doubt, the lot of many, or gid 

 would over-run our flocks to a much greater extent than now. 



There are few shepherds of experience who are not familiar 

 with the eccentricities of sturdy sheep. The onset of the 

 disease varies in different cases, and the symptoms are by no 

 means alike in all. In some the patient is dull, and hangs 

 back from the troughs. The eyes are glassy, and the face 

 wears a vacant stare. It may obstinately stand, and require 



