78 CIRCULATORY STIMULANTS 



their walls, and is seen principally in the splanchnic area, although it 

 also occurs in the limbs. These results, however, are seen in the labor- 

 atory only after toxic doses and in therapeutic doses are very slight. 



The sum of the above actions is an increased pressure in the aorta. 

 This invigorates the coronary circulation, and the prolonged dias- 

 tasis allows the heart to last longer. At the same time the increased 

 systole favors emptying of the coronary veins. The result is an 

 increase in supply of food and oxygen to the heart for nourishment 

 and recuperation, and a greater supply of the drug to the heart muscle 

 to maintain its stimulation. 



Toxic Stage. The most prominent effect of this stage is irregu- 

 larity of the heart, both in rhythm and force. In the first stages of 

 poisoning the pulse becomes slow and irregular and the output less 

 than before the drug was administered. In the second stage the 

 pulse becomes rapid, but still more irregular. The final stage of 

 poisoning shows a still greater increase in the number of beats until 

 delirium cordis takes place and the organ stops in diastole. 



Respiratory System. There is little or no action from thera- 

 peutic doses, although there may be some stimulation of the center on 

 account of the improvement of the circulation. Toxic doses stimu- 

 late the center, so that the respirations may be strong and deep, but 

 with the fall of blood pressure in the later stages the respiratory center 

 fails. 



Nervous System. There is no appreciable effect seen after 

 therapeutic doses. Convulsions are usually seen in the later stages of 

 poisoning. These are probably due to stimulation of the convulsive 

 center in the medulla and partly to asphyxia which results from the 

 poor circulation. 



Diuretic Action. Digitalis has very little effect upon the flow 

 of urine in normal animals. In heart disease, however, accompanied 

 by effusion, it is a strong diuretic. The increased secretion of urine 

 is entirely due to an increased blood pressure in the glomeruli of the 

 kidneys. The water and chlorides of the urine are especially in- 

 creased, while the other urinary constituents are but little altered. 



Temperature. Large doses reduce temperature in febrile condi- 

 tions. Toxic doses reduce it in normal animals. 



Eye. Toxic doses cause a dimness of vision and mydriasis. 



Absorption. Digitalis and its allies are slowly absorbed and 

 eliminated. They are also slow in action, both on account of the 

 tardy absorption and because their effect does not take place promptly, 

 even after they reach the blood. Consequently immediate action 

 cannot be obtained unless toxic doses are given intravenously, and 

 even then, although an animal will pass through the different stages of 

 action, death will not take place for several hours. 



No appreciable effect will follow the administration of therapeutic 

 doses for several hours, and the full effect only after it has been ad- 



