DISEASES OF THE DIGESTIVE ORGANS 41 



purgatives: sodium sulphate, potassium sulphate and magnesium 

 sulphate; also, fructus rhamni catharticae, frangula and cascara 

 sagrada. 



(c) Laxatives or Lenitives, mild cathartics, which must be 

 given in very large doses and most of which do not operate upon 

 horses and cattle. This group includes castor oil, senna, sulphur, 

 manna, tamarind, syrup, honey, glycerin, and the fixed oils. 



Theories Regarding Catharsis. — ^The question of how and in 

 what manner catharsis is brought about after the administration 

 of a cathartic has been answered in many different ways. A num- 

 ber of theories have been proposed by Liebig, Buchheim, Aubert, 

 Voit, Hay, Brieger, Radziejewski, and others. From these we 

 learn that catharsis is not a simple process but a very compUcated 

 action resulting usually from several factors operating together. 



(a) According to Liebig, the neutral salts operate principally 

 in a purely physical manner, i.e., in accordance with the laws of 

 osmosis. Water passes from the blood, which is poor in salts, 

 into the intestines, which contain a large amount of salt. The 

 "animal membrane" separating the blood from the intestinal con- 

 tents is the intestinal mucous membrane. If a solution of Glauber's 

 salt or epsom salt is placed in an isolated loop of the small intestine 

 the latter will be filled to distention in a few hours with a clear 

 yellow, alkaline fluid. At the same time the mucous membrane 

 will retain its normal pale color. The fluid which passes from the 

 blood into the intestines operates as a stimulant to peristalsis and 

 diarrhoea occurs. 



(b) On the other hand, Buchheim asserts that the neutral salts 

 produce catharsis by retarding or suppressing absorption of intes- 

 tinal fluids in consequence of their slight diffusibility. The more 

 slowly and least diffusible salts, sodium sulphate, potassium sul- 

 phate and magnesium sulphate, therefore, possess a cathartic 

 action in contrast with the rapidly and readily diffusible sodium 

 chloride. Other cathartics, especially the drastics, probably re- 

 tard absorption by paralyzing the intestinal epithelium and villi. 



(c) Peristalsis is reflexly stimulated and accelerated through 

 the direct stimulation of the nerves in the intestinal mucous mem- 



