Aperients, or purges are those medicines which quicken or increase the evacuations from the bowels, varying, however, a good deal in their mode of operation. Some act merely by exciting the muscular coat of the bowels to contract; others cause an immense watery discharge, which, as it were, washes out the bowels; whilst a third set combine the action of the two. The various purges also act upon different parts of the canal, some stimulating the small intestines, whilst others pass through them without affecting them, and only act upon the large bowels; and others, again, act upon the whole canal. There is a third point of difference in purges, depending upon their influencing the liver in addition, which mercurial purgatives certainly do, as well as rhubarb and some others, and which effect is partly due to their absorption into the circulation, so that they may be made to act by injecting into the veins, as strongly as by actual swallowing and their subsequent passage into the bowels. Purgatives are likewise classed, according to the degree of their effect, into laxatives acting mildly, and drastic purges acting very severely.

1. Strong Aperient Bolus

Calomel, 4 grains; jalap, 14 to 20 grains. Linseed meal and water, enough to make one or two boluses, according to size.

2. A Good Aperient Bolus

Blue pill, § scruple; compound extract of colocynth, 1 scruple; powdered rhubarb, 5 grains; oil of aniseed, 2 drops. Mix, and give to a large dog, or divide into two or three for medium-sized or smaller ones.

3. Castor Oil Mixture

Castor oil, 1/2 pint; laudanum, 1/2 ounce; oil of aniseed, 1 drachm; olive oil, 2 ounces. Mix, and give one, two, or three table-spoonsfuls, according to the size of the dog.

4. Purgative Injection

Castor oil, 1/2 ounce; spirit of turpentine, 2 drachms; gruel, 6 to 8 ounces. Mix.