ACIDUM GALLICUM. 339 



testines, -where it and its compounds are the most popular 

 remedies for diarrhoea, whether alone or combined with 

 other astringents, antacids such as chalk, or anodynes such as 

 opium. Intestinal haemorrhage may sometimes be arrested 

 by the same means. During its passage along the alimentary 

 canal, part of the tannin is converted into gallic acid, which 

 enters the blood ; the rest is excreted in the faeces. 



Tannic acid + water = gallic acid -f glucose. 



CszHaaOw + 4H 2 = 3H 3 C 7 H 3 5 + C 6 H 1? 6 . ^ 

 Gallic acid possesses no local astringent or antiseptic pro- 

 perties, and is therefore seldom if ever given for immediate 

 local purposes. 



2. ACTION ON THE BLOOD, AND ITS USES. 



Entering the circulation as gallic acid, the preparations of 

 tannin are not certainly known to have any further astringent 

 effect on the vessels, any antiseptic action, or coagulating in- 

 fluence on the blood. If injected directly into the veins, 

 tannic acid would prove rapidly fatal by clotting and embo- 

 lism. 



3. SPECIFIC ACTION AND USES. 



The action of these substances on the tissues must depend 

 entirely on the gallic acid. In full doses gallic acid causes 

 circulatory depression, by weakening the heart and dilating 

 the vessels ; and it also causes dyspnoea. But besides these 

 effects determined by experiment, it is almost universally re- 

 garded to be a specific astringent and haemostatic, and thus to 

 arrest chronic discharges from internal and distant parts, such as 

 the uterus and rectum, and to check bleeding, especially haemop- 

 tysis. Gallic acid is much used for these purposes, and should 

 be given in full doses even up to one drachm at a time if 

 haemorrhage be urgent. It must be confessed that some 

 authorities do not believe in this action or use of the drug. 



4. REMOTE LOCAL ACTION AND USES. 



Tannic and gallic acids are rapidly excreted, chiefly as 

 gallic acid, partly also as pyrogallic acid, in the urine, which 

 is darkened in tint. No remote disinfectant effect is to be 

 obtained in the kidneys or bladder; nor is gallic acid now 

 believed to diminish the albuminuria of Bright's disease. Some 

 hold that it arrests renal haemorrhage ; but in this, and in all 

 kinds of haemorrhage, there is a constant possible source of 

 error, from the fact that the spontaneous arrest of bleeding is 

 extremely common. 



Gallic acid has also been used in night-sweats, with doubt- 

 ful success. 



