Drugs are administered by way of the rectum when the animal can not be drenched, or the drug can not be given in any other way and when a local action is desired. An _enema_ or _clyster_ is a fluid injection into the rectum and is employed for the following purposes: to accelerate the action of a purgative; to stimulate the peristaltic movement of the intestines; to kill intestinal parasites; to reduce body temperature; to administer medicine; and to supply the animal with food. An enema may be administered by allowing water to gravitate into the rectum from a height of two or three feet or by using an injection pump. In the larger animals several feet of heavy walled rubber tubing carrying a straight nozzle at one end should be used. In administering an enema, the rectum should be emptied out with the hand and the nozzle of the syringe carried as far forward as possible. The operator should be careful not to irritate or tear the wall of the rectum. Size of the Dose.--The doses recommended in the treatment of the different diseases, unless otherwise stated, are for mature animals. The dose for a colt one year of age is about one-third the quantity given the adult, two years of age one-half, and three years of age two-thirds. In well-matured colts a larger dose may be given. In cattle, the doses recommended are about the same. In the smaller animals the size of the dose may be based on the development and age of the animal. When the drug is administered at short intervals or repeated, the size of the dose should be reduced. The physiological action of some drugs may be changed by varying the size of the dose. QUESTIONS 1. Give a general description of preventive treatment. 2. By what channels may drugs be administered? 3. How are drenches administered? 4. How are solid drugs administered? 5. What kind of drugs are administered hypodermically? 6. What is an enema? 7. What proportion of the dose of a drug recommended for the adult may be given to immature animals? PART II.--NON-SPECIFIC OR GENERAL DISEASES CHAPTER IV DISEASES OF THE DIGESTIVE SYSTEM