252 SPECIFICS FOR THE ALIMENTARY TRACT 



to be of uncertain action in the horse and dog. Scammonia is one 

 of the oldest drastics. Its use dates back to the time of Hippocrates 

 but has been about abandoned. 



Other drugs of this group are: Leptandra (Culver's Root), 

 Iris (Blue Flag), Stellingia (Queen's Root) and Juglans (Butter- 

 nut). These drugs are rarely used in veterinary medicine. 



f. SALINES 



The most prominent members of this group are sodium sulphate, 

 magnesium sulphate, potassium sulphate, sodium and potassium tar- 

 trate, potassium bitartrate and mag-nesium oxide. 



The salines differ from the vegetable purgatives in being but 

 feebleirritants to the intestines. It was formerly believed that the 

 salines stimulated more or less secretion from the intestinal canal, 

 while their slow diffusibility impeded the absorption of the secreted 

 fluid and it was on this account that they were recommended to be 

 given in concentrated solutions. It has been shown that this theory 

 was wrong, because the purgative action is not proportional to their 

 endosmotic equivalent. 



All saline substances are not absorbed at the same rate. Some 

 are rapidly taken up from the stomach and intestines, and others so 

 slowly that they reach the large intestines before any appreciable 

 absorption has taken place. The kation magnesium is absorbed the 

 most slowly, calcivim, a little more readily and those of potassium, 

 sodium and lithium, about equally but more rapidly than calcium. 



The chlorides are the anions absorbed most rapidly, then come 

 the bromides, iodides, nitrates and lastly the sulphates, the last- 

 named being almost entirely excreted by the rectum. The cathartic 

 action of an ion depends on the time required for its absorption, the 

 slower the absorption, other things being equal, the greater the pur- 

 gative effect. 



On account of their being nonabsorbable, these salts exert their 

 osmotic properties in the following ways: If a concentrated solu- 

 tion of a slightly diffusible (absorbable) salt is taken into the 

 stomach, it becomes diluted with the liquid present, or if the stomach 

 was empty it draws fluid from the cells of the stomach, causing irri- 

 tation, with nausea and at times even vomition. 



The rate of the dilution in the stomach, in the absence of fluid 

 present, depends somewhat upon the amount of fluid in the blood 

 and tissues. If they contain large quantities of fluid, the dilution 

 will be fairly rapid and when the solution has become fairly diluted 

 it will pass on into the small intestines. However, if the blood and 

 secretions do not contain fair amounts of water, the dilution is slow 

 and vomiting may take place, but if water is freely supplied, the 

 nausea is not so marked and may not be seen. 



Upon reaching the intestines the solution retains its water until 



