250 VETEEINAEY TOXICOLOGY 



widely distributed and well known, a particular description 

 is unnecessary in this place. In the United States the 

 plant is cultivated, and is naturalized to some extent on 

 Cape Breton Island. 



Active Principles. — All parts of the fox-glove contain 

 the digitalis glucosides, the second year's leaves being 

 richer than the first. Neither boiling nor drying deprives 

 the plant of its activity. At least four constituents have 

 been characterised as components of digitalis. These are : 

 (1) Digitalin, insoluble in water, soluble in alcohol, acting 

 as an irritant and heart poison. It is prepared from the 

 seeds. (2) Digitoxin, having similar solubilities, is the 

 most active heart poison, and forms from 0"25 to 0"3 per 

 cent, of the wild plant. (3) Digitale'in, soluble in water and 

 alcohol, has similar effects. (4) Digitonin, sparingly soluble 

 in all solvents, is a colloidal glucoside resembling saponin, 

 and is not a heart poison. 



Tinctures and extracts of digitalis vary in their composi- 

 tion ; thus, French digitalis made from the leaves contains 

 chiefly digitoxin, and German digitalis, from the seeds, owes 

 its activity chiefly to digitalin, but also contains about 50 per 

 cent, of digitonin. Pure digitalin is known as digitalinum 

 verum. 



Toxic Doses.— Cornevin gives the toxic amounts of the 

 green leaves as — 



4-5 ounces for the horse. | 1 ounce for the sheep. 



6-7 „ „ ox. I i-f „ „ pig. 



Kaufmann gives 1 ounce of the powdered leaf as poisonous 

 to the horse, 80 to 130 grains to the dog, and 30 grains to 

 the cat. Of digitalin 2^ grains for the horse, i grain for the 

 dog, and ^- grain for the cat. 



Effects. — Apart from the irritant effects, the chief action 

 of digitalis is upon the heart, causing increased and pro- 

 longed systole, with diminished and shortened diastole. In 

 poisoning the heart is arrested in systole. The drug is a 

 powerful diuretic, and owed its introduction into thera- 

 peutics to this effect. Digitalis is a cumulative poison, 



