443 VEGETABLE DRUGS 



adrenalin but, when injected into the bloody the* action is less powerful 

 and of much longer duration. 



Constriction of the blood vessels of the belly and limbs with stimula- 

 tion of the heart, constitutes the chief action on the circulation. This is 

 brought about by the stimulating effect of ergotoxine on the vaso-con- 

 strictor nerve endings, especially of the sympathetic nerves from the 

 thoracic and lumbar spinal cord. There is great rise in blood pressure, 

 as always occurs when the vaso-constrictors of the splanchnic area are 

 stimulated. Stimulation is followed by paralysis of the splanchnic ves- 

 sels, after large doses. 



Tyramine given intravenously produces marked rise in blood pres- 

 sure lasting 4 or 5 times longer than that from adrenalin. It constricts 

 blood vessels, locally and generally, and its effects are so lasting that it 

 may cause local gangrene. By the mouth, or subcutaneously, its action is 

 much less noticeable. 



The rate and force of the heart are augmented by stimulation of 

 the heart muscle or accelerator nerve endings (tyramine). This is fol- 

 lowed by slowing of the heart caused by stimulation of the vagus, centre 

 by the increased blood pressure. After large doses there is depression of 

 the accelerator nerve endings in the heart (ergotoxine). While such are 

 the actions of the alkaloids yet, when the whole drug is given intraven- 

 ously, there may be a rise or fall of blood pressure owing to other 

 principles. 



And, when ergot is given by the mouth, the effect of medicinal doses 

 in increasing blood pressure is so feeble as to be of no therapeutic value. 

 Ergot produces practically no constriction of the blood vessels when local- 

 ly applied to the mucous membranes, and for this reason it can be given 

 by the mouth and subcutaneously, whereas the constriction induced by 

 adrenalin is so great that its absorption is prevented and its systemic 

 action is only fully shown when it is given intravenously. 



Nervous system. — The nervous system is not affected by medicinal 

 doses of ergot, nor by large single doses of the drug. Certain changes 

 occur in poisoning, but these are not understood. 



Respiration. — Toxic doses of ergotoxine, intravenously, depress the 

 respiratory centre, and the breathing becomes slow and shallow, while 

 asthma is caused by ergamine intravenously from stimulation and con- 

 striction of the bronchial muscle. 



Uterus. — The most important action of ergot is that on the womb. It 

 stimulates rythmical uterine contractions by the paramount effect of the 

 drug in directly stimulating the uterine muscle. Which of its alkaloids 

 is chiefly responsible for this effect is uncertain. Tyramine is said to 

 stimulate the inhibitory fibres of the hypogastric nerve and while its 

 action is commonly overcome by ergotoxine and histamine yet in the non- 

 pregnant cat it may lead to relaxation of the womb, when given alone, 

 because the inhibitory nerves predominate. Contractions ordinarily alter- 

 nate with relaxation of the womb under the influence of ergot, but after 

 large doses the contraction may last many minutes. Ergot acts most 

 powerfully on the pregnant uterus and may cause abortion. On the non- 

 pregnant uterus it has less effect but is clinically of value in improving 



Digitized by Microsoft® 



