DIGITALIS 77 



Circulatory System. Here we get the principal action of the 

 drug and may conveniently divide the action or effect into two stages, 

 the therapeutic and toxic. Medicinal (therapeutic) doses of the drug 

 slow the heart, increase its force and raise blood pressure. The di- 

 minished frequency of the pulse is due to stimulation of the vagus 



Fig. 10. — Action of digitalis. Marked toxic Action. 



(Reproduced, by permission, from Pittenger's Biocljemie Drug Assay Methods. Published 

 by P. Blakiston's Sons and Co.) 



Fig. 11. — Action of digitalis: to.xic stage. Delirum cordis preceding the death 

 of the animal about 5 minutes. Note the weakness of the contractions and 

 extreme irregularity. 



(Reproduced, by permission, from Pittenger's Biochemic Drug Assay Methods. Published 

 by P. Blakiston's Sons and Co.) 



centers ; the increased force of the heart beat is due to direct action 

 upon the cardiac muscle, while the blood pressure is raised on account 

 of the increased force of the heart, together with a constriction of the 

 blood vessels. The constriction of the blood vessels is shown by the 

 fact that blood pressure will rise before any effect is shown on the 

 heart. The constriction of the arteries is due to direct action upon 



