Gid — Inlestinal Worms 341 



are convulsions and trembling of the muscles. The 

 animal gradually becomes weaker, until it is unable to 

 walk, and finally dies. 



In rare cases, the larvae have been removed surgically 

 by cutting out a section of the skull -bone. But the only 

 practical treatment is preventive. Sheep must be kept 

 off infected pastures and away from dogs or other 

 animals that scatter the infection. The heads of sheep 

 dying from gid should be destroyed by boiling or burn- 

 ing, so that the cysts will not be eaten by dogs and 

 spread the contamination. 



INTESTINAL WORMS 



The digestive tract is frequently infested with para- 

 sitic worms. These are found particularly in the stomach' 

 and intestines. They are common in the dog, cat, pig, 

 horse and sheep, and occasionally are found in cattle. 

 In most cases, intestinal worms gain their nourishment 

 from the partially digested food, but some may live on 

 blood, or pus or serum whi<}h exudes from irritated 

 tissues to which the worm may be attached. 



Intestinal and related worms may be divided into 

 four classes: the flat, segmented, and usually long, 

 tape -worm ; the flat, lance -shaped fluke -worms, found 

 in the liver; the thorn -headed round -worms; and the 

 common round-worms. 



The tape -worms (Fig. 53) are usually long, often mea- 

 suring many feet, but in some cases they may not be over 

 a half inch in length. Part of their life -history is as fol- 

 lows : The adult worm infesting the intestine of the host 



