=Hair Balls.= These are common in the rumen of cattle and have been found in the fourth stomach. They are especially injurious to young animals by reason of their irritating the gastric mucosa, but they also occasionally block the pylorus, producing indigestion, gastric dilatation, gradually advancing emaciation and even a fatal result. =Wool Balls.= These are found in sheep and are especially injurious in young lambs. =Bristle Balls.= These are found in swine as round, or ovoid balls or long ellipses bent upon themselves. The sharp projecting ends of the bristles render them very irritating, especially to young pigs. All of these are caused by licking themselves or their fellows, and particularly during the period of moulting or as the result of some skin affection. Lambs which are nursed by ewes with an excess of wool on and around the mammæ, and old sheep with a disposition to eat wool are frequent victims. =Cotton Balls.= These have been found in lambs fed on cotton seed cake. A certain amount of the cotton fiber is incorporated in the cake, and this is rolled together and felted by the movements of the stomach and agglutinated by mucus. =Clover-hair Balls.= The fine hairs from the clover leaf have been found rolled into balls in the abomasum of lambs producing all the evil effects of the other pilous masses. =Oat-hair Balls.= The fine hairs which cover the seed of the oat are found matted together and cemented by mucus in the stomach of horses fed on the _dust_ of oatmeal mills. They are especially common in Scotland, where oatmeal has been so extensively used. =Paper-ball.= In the museum of the N. Y. State Veterinary College is a conglomerate ball of paper taken from the stomach of a hog by Dr. Johnson, Sioux City. =Phosphatic Calculi= have been described as found in the stomach, but this is evidently an error, as the acid secretion would have speedily dissolved them. The error doubtless came from mistaking the transverse colon for the stomach. =Sand and Gravel= arrive in the stomach of the _horse_ from pasturing on loose sandy land, the plants being pulled up by the roots and swallowed together with the sand adherent. Also from drinking water from shallow streams with sandy bottoms. Feeding of grain from the ground is a cause of swallowing sand, earth and pebbles. Licking the soil in acidity of the stomach is another cause. Fodder that has been packed down and mixed with earth, and that which has been blown full of sand or dust, and roots eaten from the ground in wet weather lead to the ingestion of much sand or earth. Shetland ponies taken from the islands pass sand for some weeks. Dogs taught to fetch and carry, swallow stones, pebbles, marbles, etc., accidentally. =Nails, Wires, Needles, Pins, etc.= More or less pointed metallic objects are often taken in with the food by gluttonous horses and though usually arrested in the intestines they sometimes irritate or wound the stomach.