174 DISEASES OF SWINE 



both extremities. The average length is about half 

 an inch. The female is larger than the male. 



Source of Infection.— This species of intestinal 

 worm is very widely distributed. Infection and re- 

 production occur the same as in other round worms. 

 The large is a more favorable location for parasites 

 than the small intestine, as they are situated so far 

 back that it is difficult to destroy them, and a healthy 

 digestion does not disturb their development to the 

 same extent that it does in the small intestine. 



Symptoms. — It is generally understood that pin 

 worms interfere but very little with the thriftiness 

 of their host. The worm is small, and its location 

 and habits ■are not what we expect in one causing 

 marked disturbance. Although often present in 

 large numbers, the irritation to the intestines is not 

 sufficient to cause a noticeable inflammation of the 

 lining membrane. It does not seem to cause as much 

 annoyance and restlessness as do the pin worms in 

 other species of animals. , 



Little is known regarding the symptoms of dis- 

 ease produced by the pin worm of hogs. But no 

 doubt in conjunction with other parasites it helps in 

 aggravating the symptoms of intestinal parasitic dis- 

 eases. 



THE WHIP WORM 

 Trichocephalus Crenatus — Rud. 



The whip worm is the least common of the in- 

 testinal worms of hogs. It is usually found in the 

 beginning of the large intestine (cscum), with its 

 head end firmly attached to the lining membrane. 



