lyf^ 



THE FARM DOCTOR. 



lowed by crustaceans, in which they encyst themselves anf' 

 develop the characters of the adult worm in miniature, bur 

 remain very minute and fail to attain their full size till their 

 host is swallowed by another animal. Among domestic 

 animals ducks and pigs harbour these, probably because of 



trig. 27.— Trichocephalus Affinis, 

 nat. size. 



¥\g. 26.— Ascarfs Megalacephala. F)£. 28.— Head of Taenia Expansa, 



their carnivorous appetite. The round worms mostly live in 

 their young and immature condition, out of the body, in water 

 or moist earth, or on vegetables (see lung-worms, verminous 

 bronchitis), but some are exceptions, like the common pin-worm 

 oi the horse (Sclerostomum Equinum) which lives in pill-like 



