DISEASES WHICH ARE INDUCED BY PARTICULAR PARASITES 171 



The worm varies in length from 3 or 4 inches up to a foot or more, and 

 it is occasionally present in such enormous numbers in the small intestines 

 as to fill them completely, necessarily causing a good deal of disturbance. 

 Occasionally a worm passes up the pancreatic duct, and now and then one 

 is found in the duct leading to the liver. When in sufficient numbers to 

 cause obstruction in the intestinal canal they are said to cause symptoms of 

 colic, giddiness, epilepsy, and tetanus; but when only a few are present 

 they do not seem to cause any inconvenience. The illustration repre- 

 sents the general form of these worms of small 

 dimensions (fig. 274). 



Various remedies are used for the expulsion of 

 these worms, among them arsenic, calomel, tartar 

 emetic, carbolic acid, turpentine; and recently san- 

 tonine has been employed, and has proved to be 

 more reliable than any of the other agents. The 

 dose for a horse is 15 grains in a ball, with 3 or 

 4 drachms of aloes. The medicine should be re- 

 peated in a week. 



Another of the nematode worms is the whip- 

 worm [Oxyui-us curinda), which infests the large 

 intestines and occasionally excites irritation of the 

 anus, which is indicated by the horse constantly 

 rubbing the tail. A marked symptom of the 

 presence of oxyurides is the accumulation of 

 yellow dust -like matter around the anus. This 

 is made up of the eggs of the parasite. 



The expulsion of these worms is much assisted by occasional 

 enemas of salt and water. An illustration of this worm is given 

 in fig. 275. 



Two other nematode worms are found in the intestine of 

 the horse. Both of them deposit their eggs beneath the mucous 

 giving rise to small tumours. The two parasites are known as 

 (I) the Strongylus armatus and (2) the Strongylus tetr acanthus. The latter 

 is the most common and the most destructive. The Stro^irjylus armatus is 

 •distinguished by its large mouth, which is armed with a row of cutting teeth 

 arranged close together. The Strongylus tetracanthus has, in addition 

 to the row of teeth like the Strongylus armatiis, four large spines, from 

 which the name is derived, and also inside the mouth a row of sharp 

 books. It will be evident, therefore, that the creature is well provided 

 with offensive weapons. The worm is constantly found accumulated in 

 the large bowel, frequently in company with the Strongylus armatus. 



Fig. 275.— Oxy- 



urus of Horse — 



Female 



{natural size) 



vn. Vulva. 

 a. Anus. 



Fig. 274. 



Ascaris (about 



^ nat. size) 



Tuembrane, 



