100 



VETERINARY MEDICINE AND SURGERY. 



WORMS. 



Head. 



Etiology. — These are introduced 

 from Avithout in either the food or 

 drink. A low condition of the system, 

 pasturing in marshy or wet ground, or 

 the use of stagnant waters are undoubt- 

 edly predisposing causes. Young animals 

 are more subject to them than old ones, 

 and weakly more than the strong. They 

 are, however, often found in horses in 

 which neither of these conditions exists. 

 Worms derive their nutriment by 

 suction from the intestinal secretions 

 and die if the animal dies. 



Three kinds are commonly found in 



the horse: first, the Ascaris himbricoides 



or Megalocephalus, or long round worms, 



frequently discovered in the dung. They 



inhabit the small intestines, and are 



sometimes twelve inches long (Fig. 67). 



Second, the Oxyuris vermicularis, a 



small, needle-like, lively worm, found in 



Male. tS great numbers in the large intestines 



and rectum. This worm is usually white 



in color and about half an inch long 



(Fig. 68). Third, the Trichocephalus dispar, a slender 



worm measuring from two to four inches in length, and 



consisting of a rounded body for half its length, with a 



contracted, thread-like head. These are found in the large 



intestines (Fig. 69). Tape worms are occasionally found 



in young and feeble animals. 



Symptoms. — The only certain evidence of worms is 

 their detection in the dung. In many cases, their pres- 

 FiG. 67. ence can only be suspected by a peculiar hard, dry, rough 

 coides, female, appearance of the coat, or at other times by frequent 



