PARASITIC DISEASES 1^3 



testines are badly irritated and inflamed by either 

 the common round or thorn-headed worm, they 

 tear easily when handled, because qf the inflamma- 

 tory changes. The wonns may drop through the 

 torn part into the albdominal cavity, and the break 

 in the wall is mistaken for a perforation. Stock- 

 men frequently describe such post mortem lesions in 

 hogs. 



The disturbance in nutrition and the class of 

 symptoms shown by the hog depend on the number 

 of worms present. In most cases the animal does 

 not harbor more than three or four, and these are 

 often associated with other forms, generally common 

 round worms. Badly infected pigs are said to show 

 an irregular appetite, constipation, diarrhoea, severe 

 pain, and marked unthriftiness. Most, writers con- 

 sider the nervous symptoms of most importance. 

 However, the symptoms shown do not differ greatly 

 from those, resulting from the presence of round 



.worms. 



THE PIN WORM 



CEsophagostoma Dentatum — Rud. 



The pin worm is a very common parasite in hogs. 

 It is usually found in large numbers toward the be- 

 ginning of the large intestine (caecum and double 

 colon), mixed with the intestinal contents and be- 

 tween the folds of the lining membrane. It is a 

 small worm, and unless looked for carefully escapes 

 notice. 



Description. — The 'body of the pin worm is white 

 or grayish brown in color, straight and pointed at 



