310 MATERIA MEDIC A AND THERAPEUTICS. 



crystalline prisms, also very bitter. It is now known to be a 

 compound of four bodies, namely, (1) Digitalin proper, insoluble 

 in water, forming the bulk of Homolle's digitalin ; (2) Digitale'in, 

 very soluble in water ; (3) Digitoxin, insoluble in water, and 

 the chief constituent of Nativelle's digitalin ; and (4) Digitonin, 

 probably the same as saponin, the active principle of senega. 

 Digitalem seems to possess the properties of a mixture of 

 digitalin and digitonin. Digitoxin is by far (7 times) the 

 most powerful, a local irritant, and a muscular depressant ; and 

 therefore, and because insoluble, unfit for use. None of the 

 constituents are so suitable as digitalis leaf itself. 



Incompatibles. Sulphate and tincture of iron, acetate of 

 lead, and preparations of cinchona. 



Preparations. 



1. Digitalinum. Digitalin. A complex active substance 



obtained from digitalis. Source. Made from (1) an 

 alcoholic extract, by dissolving out the Digitalin with 

 Acetic Acid and Water ; (2) decolorising with Char- 

 coal ; (3) precipitating the impure Digitalin with 

 Ammonia and Tannic Acid ; (4) removing excess of 

 Tannic Acid by Oxide of Lead; (5) dissolving in 

 Spirit; and (6) purifying with Charcoal and Ether. 

 Characters. Porous mamillated masses, or small scales, 

 white, inodorous, and intensely bitter. Dose, -fa to 

 7&gr. 



2. Infusmn Digitalis. 1 in 160. Dose, 2 to 4 fl.dr. 



3. Tinctura Digitalis. 1 in 8. Dose, 5 to 30 min. 



ACTION AND USES. 

 1. IMMEDIATE LOCAL ACTION AND USES. 



Externally, digitalis has a slightly irritant action ; it is 

 probably not absorbed by the unbroken skin. 



Internally, in full doses, it deranges the stomach and bowels ; 

 dyspepsia, vomiting, and occasionally diarrhoea following its 

 continued use in small doses effects which are partly local, 

 partly specific, and to be carefully avoided or checked in 

 practice. 



2. ACTION IN THE BLOOD AND SPECIFIC ACTION. 



The active principles of digitalis enter the blood freely. 

 Thence they reach the tissues more quickly than they leave 

 them ; and doses, however small, if closely repeated, tend to 

 accumulate in the body. The action of digitalis is mainly 



