See Bowels, Obstruction of. This is a slipping of one portion of the intestines that has been contracted by spasm, within another part retaining its natural diameter, and is another and not uncommon cause of obstruction, and apt to occur during spasmodic colic. It is fatal, and can not be determined by symptoms, a postmortem only showing the trouble. No dog should be allowed to be costive over two days, and not so long, is much safer, without having been helped by proper remedies prescribed elsewhere. It is always safe, however, and advisable to give in such cases a full dose of castor oil, olive oil or a mixture of both. Worms can cause obstruction in the intestines, especially in puppies, round worms getting coiled up into balls, which sets up local irritation, interfering with the natural action of the bowels.