336 MANUAL OF EQUINE MEDICINE. 



inch wide, and is provided with four suckers, a double 

 coronet of booklets, between thirty and forty in number, 

 and a central rostellum. 



The fourth stjgment is as long as all the rest of the worm ; 

 and is alone supplied with sexual organs. 



The cyst, larval form, or hydatid, which has received the 

 name of echinococcus veterinorum, is characterized by almost 

 indefinite increase in size, and by almost indefinite multipli- 

 cation by the formation of gemmae. 



This cyst, in its early form, is small and globular, with 

 transparent walls and finely granular contents. In its later 

 stages, when it has much increased in size, the walls become 

 thick and the contents fluid. 



The colourless fluid and limpid contents contain a quantity 

 of salt, and usually no albumen. 



The walls are composed of two coats, an outer, which is 

 fairly thick, transparent, elastic and laminated, and an inner, 

 which is thin, and made out of fine cells, sometimes contain- 

 ing oval or globular refractive bodies. 



In some cases the hydatid is only increased in size, but 

 as a rule secondary cysts form in the substance of its walls. 

 The cysts grow — some towards the outer aspect, some in 

 the mid-region, and some towards the inner aspect, and 

 often in connection with the cellular laminae. 



The secondary cysts often repeat in their growth all the 

 characters of the parent hydatid. 



This hydatid may be found in various organs and glands 

 of the body, especially the lungs, liver and kidneys, and 

 sometimes in the brain. They vary much in size, sometimes 

 being as small as a pea, and occasionally encountered as 

 large as a good sized cocoa-nut. They may or may not 

 produce symptoms which vary according to the organs 

 affected, and the size and exact position of the cyst. 



2. CCENURUS CEREBRALIS.— This hydatid is the larval 



