233 SPECIFICS FOR THE ALIMENTARY TRACT 



7. PURGATIVES AND CATHARTICS 



Cathartics or purgatives are agents which quicken or increase 

 the evacuation from the bowel. They may produce this action (1) 

 by direct irritation of the mucous membrane of the intestine; (2) 

 by increasing the fluid of the feces, or (3) by stimulating the nerve 

 endings in the intestinal walls with resulting peristalsis. In all 

 cases peristalsis is increased. In the first place, the increased per- 

 istalsis is due to direct irritation of the mucous membrane; in the 

 second place it is increased indirectly by distending the bowel with 

 an increased amount of material, and in the last place by directly 

 stimulating the nerve endings supplying the muscles of the intes- 

 tine. 



The vegetable purgatives, with the exception of the alkaloidal 

 rapid purgatives, act through their irritant properties, and in some 

 cases only after they are acted upon by the secretions of some of the 

 glands. (Castor oil.) In moderate doses, the purgatives simply 

 hasten the normal movements of the intestines and the stools are of 

 the ordinary appearance and consistency. In increasingly larger 

 doses they become of a softer consistency and even watery. Their 

 action is usually accompanied by some colicky pain and the rapid 

 movements of the intestinal contents are shown by the characteristic 

 gurgling sounds. Large amounts of powerful purgatives cause all 

 the symptoms of gastroenteritis. The stools in these cases at first 

 contain the ordinary fecal matter, with more than the usual amount 

 of fluid, but later consist almost entirely of blood-stained mucus, 

 with little or no resemblance to fecal matter. This violent purga- 

 tion is accompanied by other symptoms of gastroenteritis and may 

 result in shock, collapse and finally death. 



ISTeutral fats and saponified oils like butter, lard and olive oil 

 pass practically through the stomach unchanged but are more or less 

 completely saponified in the small intestines, and the resulting soaps 

 may be sufiiciently irritating to the intestinal mucous membrane to 

 cause increased peristalsis and with the excess of the fat or oil act 

 as a mild laxative. 



The source of the increased fluid in the feces foUovnng purga- 

 tives has received a great deal of discussion. According to some 

 authorities, purgatives simply accelerate the passage of the intes- 

 tinal contents so that there is no time for absorption of the fluid and 

 the feces are passed in the fluid condition in which they exist in the 

 small intestine. Others hold that purgatives cause fluid to pass into 

 the intestines either by increasing the normal secretions or by caus- 

 ing an inflammatory exudate from the vessels. Both have, to a 

 certain extent, proved their theories by injecting purgatives into 

 loops of the intestine isolated from the rest of the bowel. The con- 

 tradictory results are probably due to different methods of investi- 



