526 HORSE, SWINE AND POULTRY DISEASES 



cine, which is best given in a thin slop. Santonin is a dangerous 

 drug unless used strictly in the proportions given. (Wis. B. 184.) 



COMMON ROUND WORM. 



The natural habitat of the common round worm is the small 

 intestine. It is sometimes found in the large intestines and the 

 stomach. Its presence in the stomach occurs only when the hog is 

 dead, and is reached by a reverse peristalsis of the intestines or the 

 movement of the worms themselves. When quite active and present 

 in large numbers, they may work forward into the oesophagus. It 

 is not uncommon to find them extending into the common bile 

 duct, some even enter the gall bladder, while others imbed them- 

 selves in the ducts coming from the various lobes of the liver. In 

 young and unthrifty pigs round worms are common parasites, and 

 it is not unusual to find from ten to twenty of them in a single in- 

 dividual. They may be present in such numbers as to almost fill 

 the lumen of the intestines for several feet of its length. There are 

 few pigs over the country that do not harbor this parasite to a greater 

 or less extent. Men who treat hogs for cholera and swine plague 

 are quite familiar with this worm, and report it as being quite 

 common. 



Description. The Ascaris suilla, Dujardin, is a large round 

 worm, tapering at both ends, and white, or yellowish white in color. 

 The body is firm and elastic, the digestive tract quite complete. 

 The average length of the female is ten inches, that of the male six 

 and a half inches. The head is small and armed with three lips, 

 the upper one having a papillae at each of its inferior angles, the 

 other two at the middle of their base. The female organs consist of 

 a pair of convoluted tubes, each dilating into a uterus and uniting 

 to form a single tube, the vagina. The opening from the vagina, the 

 vulva, is situated toward the anterior third of the body in the middle 

 of an annular constriction. The male organs are simple, consisting 

 of a single convoluted tube dilated below to form a seminal vesicle, 

 and terminating in an ejaculatory duct which opens into the clo- 

 aca. The posterior extremity is furnished with a large number of 

 papillae, some of which are back of the anus. The ova are about 

 one four-hundredths of an inch in length. 



Source of Injection. The eggs of the ascaride are passed out 

 with the excreta and drop to the ground. Moisture and warmth are 

 necessary for their hatching, but they seem to be able to live under 

 unfavorable conditions and will resist drying for some time. When 

 the conditions are favorable, the eggs hatch and the pig becomes in- 

 fected by taking the immature form into the digestive tract along 

 with the food, or the embryo, when well formed in the egg, reaches 

 the digestive tract with the food, the shell is dissolved by the gastric 

 juice and the embryo liberated. Earth eating pigs are almost sure 

 to become infected. Feeding hogs on dirty feeding floors or on the 

 ground, and drinking from ponds and dirty watering troughs are 

 common sources of infection. The best of hygienic conditions may 

 not prevent infection, but will greatly lessen it. 



