ACTION AND USES OF MEDICINES. 147 



290. Saline substances. 



Saline substances, such as Sulphate of Magnesia or Epsom Salts, are 

 also used as purgatives. In addition to their purgative properties, they 

 seem to alter the condition of the blood and to diminish its tendency to 

 coagulation in certain diseases. Hence in fevers they are often adminis- 

 tered with benefit ; but as a general rule they are neither so safe nor so 

 certain in their action as aloes. 



291. Clysters or Enemata. 



Clysters, otherwise called Enemata, soften and loosen the hardened 

 faeces, and also by mechanically distending the lower gut cause it to 

 evacuate its contents. The excitement of the lower intestines sometimes 

 extends forwards and rouses the small intestines to action. The water 

 should be of the temperature of new milk. The quantity of water thrown 

 up at one time should not exceed quarts. No violence should be used 

 in forcing it up. Whether the instruments used are the ordinary syringe, 

 patent pump, common bladder, or leather bag and funnel pipe, the fluid 

 should invariably be injected gently and gradually. The object of an 

 enema is not to wash out the patient's inside, but simply to rouse the 

 powers of nature to evacuation. Purgative enemata usually consist of 

 warm water only, but if a more stimulating effect is desired, common 

 salt, oil, or solution of aloes or soap may be added. Retention for a few 

 minutes should be ensured by keeping the tail down. A second enema 

 after an interval of half an hour is generally beneficial. 



Nutritive enemata, consisting of gruel or rice water, are beneficial in 

 cases where the patient is unable or unwilling to take food by the 

 mouth. They should not exceed a quart in quantity. If larger, they 

 will probably be ejected. 



Astringent enemata, made of two drachms each of catechu and opium, 

 or a quart of starch in a gallon of water, are said to be useful in check- 

 ing diarrhoea. 



Sedative enemata are made by adding about two ounces of tincture of 

 opium to the water. They are said to be useful in allaying spasms in 

 the intestines. Their utility is, however, extremely doubtful. Gaseous 

 enemata, consisting of tobacco smoke, are also used for a similar purpose. 



Enemata consisting of two ounces of oil of turpentine, diluted with a 

 pint of olive oil, are recommended by some Veterinarians for the purpose 

 of killing worms in the large intestines. 



292. Diuretics. 



Diuretics are medicines which act on the kidneys and cause increased 

 secretion of urine. Like purgatives, they are absorbed in the blood, but 

 not being assimilated, are ejected from it and excreted through the 

 kidneys. During excretion they cause irritation, and hence produce in- 

 creased secretion. The body should be kept cool during the period of 



