448 DRUGS OF ANIMAL ORIGIN 



there is blanching of the vessels of the intestines the skeletal vessels are 

 dilated by adrenalin intravenously. 



The peculiar effect of adrenalin on the heart is due to primary 

 stimulation of the accelerator nerve endings of the heart muscle, making 

 the organ beat faster and more strongly, while the slowing is due to 

 stimulation of the vagus centre by the increased blood pressure. Acceler- 

 ation again occurs when the blood pressure falls away, and the vagus 

 ceases to be stimulated, and accelerator stimulation resumes its sway.. 

 Adrenalin also directly stimulates the heart muscle itself. The action on 

 the circulation is very transient, lasting not more than five minutes, and 

 being repeated with each new dose. 



But the predominant and most valuable effect of adrenalin consists 

 in the complete blanching of mucous membranes and raw surfaces after 

 the local application of these substances. Adrenalin is undoubtedly the 

 most powerful astringent and hemostatic known, owing to its stimulation 

 of the involuntary muscles of the blood vessels. When painted on a 

 mucous membrane or raw surface the constriction of the blood vessels 

 takes place at once and lasts for a quarter to two hours. 



Subcutaneous injection of a 1 to 1000 solution causes blanching over 

 an area about two inches in diameter within a minute and lasts for six 

 to twelve hours. Solutions containing adrenalin to the amount of 1 to 

 5000, 1 to 10,000, or even 1 to 20,000, will produce an ischemia after 

 their hypodermic use within a few minutes and lasting for three to six 

 hours. Neither ecchymoses nor sloughing occurs after the proper injec- 

 tion of the drug. Sometimes great vasodilation follows the use of 

 adrenalin aggravating congestion, or hemorrhage from the part, but this 

 is rare. 



The local constricting action is undoubtedly due to direct stimula- 

 tion of the vasoconstrictor nerve endings as it does not occur when 

 adrenalin is painted on the lung or brain since their vessels are not sup- 

 plied with constrictor fibres. 



There appears to be little or no absorption of adrenalin when it is 

 applied to mucous membranes or taken by mouth. This may be due to 

 local destruction of the drug or to vasoconstriction. Subcutaneously the 

 action is but slight on the blood vessels, more so in relaxing bronchi. 



Still more active is the intramuscular injection but the specific effect 

 on the vessels is seen in highest degree when the drug is given into the 

 veins. This must be done slowly in saline infusion to avoid heart failure 

 (left ventricle) from the great peripheral resistance resulting. For 

 these reasons the intramuscular, or better, intravenous injection is indi- 

 cated for its systemic effect. 



Bespiratimi. — Adrenalin given under the skin in small doses makes 

 the breathing deeper but, when inj ected intravenously, the respiration be- 

 comes more rapid and shallow. Adrenalin has a marked effect (Park) in 

 relaxing the bronchi, owing presumably to stimulation of the sympathetic 

 (broncho-dilator) fibres. 



Abdominal Organs. — Here stimulation of the sympathetic nerve end- 

 ings give rise to different actions according to the special functions of 

 the fibres stimulated. Thus movements of the bowels and stomach are 



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