(b) Simple Purgatives.-These are somewhat more powerful in their action than laxatives; promoting peristalsis and also increasing intestinal secretion. Some of the laxatives, as castor oil, when given in large doses, act as simple purgatives.

The simple purgatives are

(1) Aloes.

(2) Rhubarb.

(3) Frangula.

(5) Senna.

(4) Cascara sagrada.

(6) Phenolphthalein.
(7) Oxgall.

Rhubarb and senna contain chrysaphanic acid, while all, excepting phenolphthalein and oxgall, owe their purgative properties to emodin, and are often called anthracene purgatives. These are constantly prescribed, and each has its special indications, which will be pointed out when their several actions are described.

(c) Drastic Purgatives, often called Cathartics.-These cause markedly increased secretion and peristaltic movements, and in large doses severe irritation of the intestine, characterized by excessive secretion of mucus, pronounced vascular dilatation-possibly hæmorrhageand profuse, loose stools. This condition is attended with intense abdominal pain and tends to produce collapse. It is customary to prescribe hyoscyamus or belladonna with these drugs, calomel excepted, on account of the irregular peristalsis and severe griping pain which would otherwise be induced.

The drastic purgatives are as follows:

(1) Calomel.

(2) Podophyllum.

(3) Jalap.

(4) Scammony.

(5) Gamboge.

(6) Colocynth.
(7) Elaterin.

(8) Croton oil.

The most powerful are placed last. Some, as jalap, elaterin and scammony, are often called hydragogue, because of the large amount of secretion which they excite.

Therapeutics. These drugs are very useful in severe constipation, and are also frequently given for the purpose of withdrawing fluid from the body in consequence of the watery evacuations they occasion. Thus, for instance, jalap is in constant use to fulfill this indication in Bright's disease.

(d) Saline Purgatives.-The action of these is obscure. They differ from the vegetable purgatives in not inducing intestinal irritation, unless when given in very large quantities. They are absorbed

from the intestine very slowly, probably because they fail to penetrate into the cells, just as the salts of the heavy metals fail to penetrate the red blood-corpuscles. There is a distinct affinity between the intestinal epithelium and sodium chloride, but only a much weaker one between it and the saline cathartics, which do not permeate it. It seems certain that these remedies very greatly increase the secretion of intestinal fluid, and hinder its reabsorption, so that a large amount of it accumulates in the intestine. Secretion goes on till the fluid in the intestine has become a 5 or 6 per cent. solution of the drug, so that if a very concentrated solution is given, much intestinal fluid is secreted, which tends to excite peristalsis mechanically, and, in addition, a salt stimulation results from the withdrawal of liquid and salts from the cells, as well as from the slight absorption of the salt itself. As a final result there are produced an increase in quantity and number of stools of a fluid consistency. It has been denied that catharsis results if the salts are injected into the blood, but in medical practice it has been repeatedly demonstrated that magnesium sulphate, administered hypodermatically, purges. It is possible that other salines may act similarly.

The saline purgatives are(1) Potassium and sodium tartrate. (2) Potassium bitartrate. (3) Sodium sulphate.

(4) Sodium citrate.

(5) Sodium phosphate.

(6) Magnesium sulphate and other salts.

Therapeutics. These are very largely used as habitual purgatives, and such salts constitute the essential ingredients of the various mineral waters, such as Hunyadi János, Apenta, Pullna, Friedrichshall, Esculap, Rubinat Condal, Villacabras, etc. The most efficient way of using them is to add some hot water to the required dose of the salt or of the mineral water, in a tumbler and slowly sip it in the morning.

Cholagogue purgatives, so-called, will be considered under Drugs Acting on the Liver (see p. 627.)

Enemata. Any fluid preparation, injected into the rectum is called an enema. It is customary to give purgatives in this way when there is danger of their exciting nausea or when, in consequence of peritonitis or of obstruction, ulceration or other affection of the intestines, it is inadvisable to administer them by the mouth. Castor oil, olive oil, soap, aloes and magnesium sulphate are among the

substances most commonly employed for purgative enemata, enough of the vehicle selected for the injection being used to make an enema of at least 350 mils (34 pt). Such enemata act mainly by distending the bowel and thus exciting peristalsis, although the soap or other agent employed no doubt has an irritating effect in addition. A teaspoonful (4 mils) of glycerin injected into the rectum, or the same amount given as a suppository, often promptly opens the bowels. 2. Intestinal Antiseptics.-These are believed to check fermentation and putrefaction in the intestines and are

(1) Betanaphthol.

(2) Bismuth betanaphthol.
(3) Bismuth subsalicylate.
(4) Phenyl salicylate.

(5) Chlorine.

(6) Creosote.

(7) Corrosive mercuric chloride.
(8) Oil of turpentine.

Therapeutics.—Betanaphthol destroys micro-organisms in situ. Bismuth betanaphthol is nearly insoluble in water but may be partially dissolved by hydrochloric acid and does not cause symptoms of irritation. Bismuth subsalicylate has not the irritating properties of betanaphthol, but appears to be equally effective. Phenyl salicylate decomposes only in an alkaline solution, and this is useful for action in the small intestine. Chlorine water, no longer official, has been used for the disinfection of the intestines in typhoid fever. Creosote is valuable if administered in the form of enteric pills, which are soluble only in the intestinal fluids. Corrosive mercuric chloride is too poisonous for use, save in exceptional instances. Brilliant success has been achieved with oil of turpen-* tine in the treatment of typhoid fever. The intelligent use of the foregoing drugs has greatly improved the success of the treatment of the various forms of enteritis, diarrhoea, colitis, dysentery and typhoid fever.

3. Intestinal Astringents.-These may be described under the following heads:

(a) Astringents acting on the vessels of the intestine. These are the same as those acting on vessels generally. Those employed for their action on the intestine are

(1) Lead salts.

(2) Dilute solutions of silver salts.

(3) Alum.

(4) Diluted sulphuric acid.

(b) Astringents coagulating albuminous fluids and thus constricting the vessels:

(c) Astringents diminishing the amount of intestinal fluid secreted:

(1) Opium. (2) Lead salts. (3) Calcium salts.

The precise mode of action of these is obscure.

(d) Astringents diminishing the contractions of the muscular coat of

the intestines:

(1) Opium.

(2) Belladonna.
(3) Hyoscyamus.

(4) Stramonium.

(5) Lead salts.
(6) Calcium salts.
(7) Bismuth salts.

Therapeutics. The most important point in the treatment of diarrhoea is to remove the cause, if possible. Not uncommonly the cause is the presence of irritating matters in the intestine, and a mild purgative, such as castor oil or rhubarb, is indicated to remove them. In many instances a certain amount of enteritis appears to be present in diarrhoea, and remedies serving to constrict the dilated vessels and to diminish intestinal movements and secretion are called for. Hence, it is often advantageous to combine two or more astringents. Opium has long been recognized as an agent of very great value in diarrhoeal diseases, and is a very frequent ingredient in prescriptions employed for them. In such troubles, however, it is essential that the diet should be very carefully regulated, and if the symptoms are at all severe, absolute rest and attention to keeping the patient warm are called for. If there is a persistent cause, as tuberculous ulceration, palliation of the symptoms is generally all that can be expected.

E. Drugs Acting on the Liver. The liver has several distinct functions; viz.: To secrete bile, to form and store up glycogen; to form urea; to excrete substances absorbed from the intestine; and to destroy poisonous substances taken up from the intestine.

1. Drugs Influencing the Secretion of Bile.-Because an increased amount appears in the fæces it does not necessarily follow that more bile is secreted. Thus, if may be that the gall bladder and ducts have been thoroughly emptied, or that the bile which has been poured into the duodenum has been swept along quickly before re-absorption,

which is ordinarily rapid, has had time to take place. Drugs which increase the amount of bile actually secreted are called direct cholagogues. They are also sometimes spoken of as hepatic stimulants, but this is an unsatisfactory designation on account of the liver having so many different functions. Drugs which simply lead to a larger amount of bile being found in the fæces, without any additional secretion, are called indirect cholagogues.

DIRECT CHOLAGOGUES.-These have been studied in persons suffering from biliary fistula. A canula having been inserted into the bile-duct, in order to conduct the fluid outside the body, the amount of bile secreted before and after the administration of the drug under experiment is noted. A fasting state is essential because food itself causes a considerable increase in the biliary flow.

Direct cholagogues, the most powerful being placed first, are—

(1) Sodium salicylate.

(2) Sodium benzoate.

(3) Podophyllum.

(4) Corrosive mercuric chloride.

(5) Sodium sulphate.

(6) Sodium phosphate.

(7) Aloes.

(8) Colocynth.

(9) Jalap.
(10) Scammony.

(11) Rhubarb.

(12) Ipecac.

(13) Diluted nitrohydrochloric
acid.
(14) Colchicum.

There are individual differences among direct cholagogues. Some increase the fluidity of the bile, while others have the opposite effect. Sodium salicylate and sodium benzoate markedly increase both the total quantity and the solids. Podophyllum, on the other hand, increases the solids without affecting the quantity, but its purgative action is so vigorous that it is usually placed among the drastic purgatives. In fact the salicylates and, to a lesser extent, the benzoates and diluted nitrohydrochloric acid are really the only drugs of distinct cholagogue action.

INDIRECT CHOLAGOGUES.-These appear to stimulate the lower part of the duodenum and the upper part of the jejunum, thus sweeping the bile on before there is time for it to be re-absorbed.

They are- (1) Mercury, especially Calomel. (2) Most Cathartics.

Therapeutics.-Cholagogues are used in instances of digestive derangement in which hepatic disorder seems to be the cause of the disturbance, and in order to secure the excretion of the bile, as well as the secretion of a proper amount, it is often advantageous to combine direct and indirect cholagogues. Bile being a stimulant to peristalsis,