100 



The ripe proglotticls are passed out in the dog's faeces 

 and soon decay. The embryos, scattered about the pasture, 

 are swallowed by lambs or sheep while grazing ; and, 

 penetrating the intestine wall, they enter the blood-vessels, 

 and in that way reach the brain or spinal cord. In the 

 brain, the embryo becomes a big bladder- worm of the 

 coenurus type, Coenurus cerebralis, which is sometimes as 

 large as a hen's egg ; and as many as three or four hundred 

 scolices (potential tapeworms) may be formed within it. 



These hydatids in the brain of the sheep cause the malady 

 known as " sturdie " or "staggers," generally fatal; and 

 when they occur in the spinal cord, the result is " lumbar- 

 gid," a paralysis of the hindquarters. The dogs become 

 infested with the tapeworms by eating the heads of the 

 dead sheep. 



Describe Taenia echinococcus, its Larva and its Life- History. 



Taenia echinococcus is, in some parts of the world (e.g., 

 Iceland, and parts of Australia), a common tapeworm in 

 dogs. It is very small, rarely longer than five millimetres, 

 and has only three or four proglot tides, the terminal one 

 being the largest. 



The larva, an Echinococcus, lives in the liver, lungs, and 

 other organs of cattle, dogs and other domesticated animals ; 

 it also frequently occurs in Man. This hydatid " may 

 {in Man) attain the size of a child's head." The rounded 

 bladder or cyst, which contains fluid, is enclosed in a sac 

 of connective tissue ("spurious capsule ") ; and the bladder 

 wall, which is thin, consists of an outer cuticle (ectocyst) 

 and an inner germinal or proligerous layer (endocyst). 



lln domesticated animals (e.g., cattle) the bladder some- 

 times remains barren, producing no scolices (an acephalo- 

 cyst). Usually, however, a great number of brood capsules 

 arise from the germinal layer, and within these many 

 scolices are formed. The brood capsules may go free 

 and may rupture, liberating the scolices. Free brood 

 capsules and scolices in the bladder-cavity fluid are known 

 as " hydatid band." 



In Man, secondary cysts are formed in the cuticle (from 

 detached germinal parts) ; and these pass into the cavity, 



