90 MATERIA MEDICA AND THERAPEUTICS. 



nature of this action is, however, obscure. Probably the intes- 

 tinal glands are chiefly stimulated to increased secretion, and 

 the mucous membrane irritated to such a degree as to produce 

 a moderate increase of watery exudation from its vessels into 

 the bowel, peristalsis becoming more brisk at the same time. 

 The result is a thorough evacuation of the contents of the 

 small intestine as a large, loose, but not watery, stool, charged 

 with bile, which has been hurried out directly from the duo- 

 denum, and not allowed to re-enter the portal circulation by 

 absorption from the lower bowel, as it normally does. Thus 

 mercurials, especially calomel, increase the amount of bile 

 evacuated without increasing the amount secreted ; that is, 

 are indirect cholagogues by being duodenal purgatives. The 

 manner in which indirect cholagogue action stimulates the liver 

 to further secretion is discussed in Part III. The purgative 

 action of mercurials is greatly assisted by a subsequent saline, 

 such as Seidlitz powder, or the Mistura Sennae Composita. The 

 class of diseases in which mercurials are selected as purgatives 

 chiefly include cases of congestion of the portal system and 

 liver, especially those referable to secondary indigestion from 

 free living or gout ; cases of constipation attended by irritable 

 stomach, or actual ulceration of the stomach or bowels ; very 

 rarely cases of habitual constipation, except at long intervals, 

 to enable gentle laxative measures to act more freely; and 

 occasionally diarrhoaa, when it is distinctly referable to biliary 

 derangement, or the presence of an irritant in the bowel, as in 

 children. 



2. ACTION ON THE BLOOD AND ITS USES. 



As we have seen, mercury enters the blood freely through 

 the broken or unbroken skin. From the bowel but a small 

 part of a medicinal dose is absorbed, the rest passing off in the 

 faeces as the sulphide, unless combined with opium, which 

 delays its progress through the intestine. The complex mole- 

 cule which mercury forms in the stomach and intestines is 

 decomposed on entering the blood by combination with oxygen 

 and albumen, an oxyalbuminate of mercury being the result, 

 and apparently the same compound is formed when the metal 

 enters by other channels. 



No direct effect on the blood can be attributed to mercury ; 

 but impairment of nutrition generally, including digestion, 

 attends its excessive use, and induces impoverishment, both of 

 Ilic ]>lasma and the corpuscles, indirectly referable to the drug. 

 The blood under these circumstances is more watery and coagu- 

 lates less firmly, and nutrition may be further disordered in 

 consequence, with the production of low forms of inflammation 



