THE DUCTLESS GLANDS 1235 



dextrorotatory compound having only one-twelfth, the effect of the Isevo- 

 rotatory. Adrenaline is active in excessively minute doses, injection of 

 one four-hundredth of a milligramme per kilo, body weight sufficing to evoke 

 a definite rise of blood pressure. On injecting it into the circulation there is 

 immediately a rise oi blood pressure which, if the vagi are intact, is only 

 moderate in amount but is accompanied by a marked slowing of the heart. 

 This excitation of the vagus is however probably secondary to the rise 

 of blood pressure and is not due to direct action of the drug on the vagus 

 centre. If the vagi be divided, the injection of adrenaline evokes a huge 

 rise of pressure which may amount to 300 mm. Hg. It may indeed be so 

 great that the animal dies from heart failure or from pulmonary oedema. 

 The rise of pressure is observed even after destruction of the central nervous 

 system. The action is not limited to the blood vessels. It has been 

 shown by Langley and by Elliott that adrenaline injected into the circu- 

 lation arouses every activity which can be normally excited by stimulation 

 of the sympathetic system. A list of the actions of adrenaline is therefore 

 identical with a list of the chief functions of the sympathetic nervous 

 system. In the head it causes dilatation of the pupil, secretion of saliva, 

 and erection of the hairs. On the heart it has a strong augmentor and 

 accelerator influence, so that this organ beats more effectively as a rule 

 even against the enormously increased resistance offered by the constricted 

 arterioles. Whereas a rise of blood pressure generally causes increased 

 systolic volume of the heart, we may find after an injection of adrenaline and 

 during the height of the rise of blood pressure that the heart empties itself 

 more effectively than it did before, the injection. On the lung vessels 

 adrenaline has probably a slight constrictor influence. With regard to the 

 vessels of the brain, we find the same divergence of opinion as in the case of 

 excitation of possible vaso-motor nerves to this organ. Some observers, 

 on perfusing the brain with defibrinated blood, have obtained constriction 

 on adding adrenaline to the perfused blood, while others have been unable to 

 obtain any positive results in this direction. In the abdomen intravenous 

 injection of adrenaline causes complete relaxation of the musculature of 

 the stomach, small and large intestines, but contraction of the ileocolic 

 sphincter. On the bladder its effect varies according to the animal studied, 

 but in every case is identical with that obtained by stimulating the hypo- 

 gastric nerves. It has been shown by Dale that adrenaline may also excite 

 vaso-dilator fibres or produce vaso-dilator effects when such effects are also 

 obtained from stimulation of the sympathetic nerves. In order to evoke 

 these results it is necessary to paralyse the vaso-constrictors by the injection 

 of ergotoxin, one of the active principles of ergot. This drug, when injected, 

 causes first active vaso-constriction and rise of blood pressure, followed by 

 paralysis of the vaso -constrict or mechanism. Excitation of the splanchnic 

 nerves or injection of adrenaline will now bring about a fall of blood pressure 

 due to dilatation of the vessels in the splanchnic area. 



The point of attack of the adrenaline appears to be in the muscular 

 or glandular tissues themselves, since it may be obtained not only after 



