The marked stimulation of the heart and arterioles is probably due to an action on their intrinsic nervous ganglia rather than to a direct action on the muscular fibres. As previously observed by Cybulski, administration of the ex tract by the mouth or subcutaneously has very little effect on the circulation as compared to Ivhat is observed after intravenous injection. Obviously, the active principle is destroyed by the tis sues. Gottlieb (Arch. f. Exper. Path. u. Pharm., B. 38. '96).
Researches into the constitution of the blood-pressure-raising constituent of the suprarenal capsule showing that it is to be classed with the pyridine bases or alkaloids, and that it is not possible to split off pyrocateehin front the isolated active principle. This view is the op posite of that of Imam), who sup posed that the blood-pressure-raising constituent was pyrocatechin joined to some other substance, probably an acid. Abel and Crawford (Johns Hopkins Hosp. Bull., vol. viii, p. 151, '97).
The extraordinary rise in the blood pressure after intravenous injection of suprarenal extract is due to stimulation of the vasoconstrictor nerves: the centres in the brain as well as the ganglia in the blood-vessels. The suprarenal extract paralyzes the vague nerve and the car diac depressor. It, on the other hand, stimulates the central as well as periph eral ends of the accelerators. The tem porary retardation of the heart-beat is produced by the momentary stimulation of the pituitary body, which is brought about by the sudden rise of the blood pressure in the skull. Cyon (Pfieger's Arch. of Phys., vol. lxii, p. 370, 'OS).
The two drugs which most promote contraction of the arteries, and in conse quence must antagonize the dangerous fall of blood-pressure produced by chloro form, are atropine and extract of supra renal capsule. Extract of suprarenal cap sule remarkably increases the rate and the force of the heart-beat. Sett:ger (Lancet, Feb. 5, 'OS).
The most useful application of the suprarenal extract will be in cases of cardiac weakness and threatening col lapse. Mankovsky (Russian Arch. of Path. Clin. Med. and Bect., Mar., '98).
The medulla of suprarenal capsules contains a ebromogen, possibly allied to tannin in coffee, and an active principle which chemically appears to be closely connected with piperidine. This latter has a remarkable effect upon the mus cular tissues, generally increasing their t one. and producing, when injected in travenously, an enormous rise in blood pressure. Swale Vincent (Birmingham Sled. Rev., vol. xliii, No. 236).
Experiments of lad] and of Gottlieb repeated. Conclusion that the use of suprarenal gland in the lower animals does much toward preventing accidents during the administration of chloroform, probably through its powerful influence on the vascular system. Minkowsky (Revue de Then Ther. Gaz., Dec. 15, '98).
Suprarenal extract in dogs stimulates the vagus centre, thus inhibiting the heart. It produces also a direct stimula tion of the heart-muscle, resulting, when the vague influence is removed, in an in crease in the force and frequency of its beat. Accompanying the heart-action there occurs a rise in the systemic blood pressure due to the contraction of the arterioles. The pressure in the pulmo nary arteries, however, is not raised, these vessels not being acted upon as arc the others. Wallace and Mogt (Boston Med. and Surg. Jour., Jan. 26, '99).
Epinephrin, the active principle of the adrenals and the commercial adrenalin, may practically be considered alike. Injected subcutaneously, intravenously, intraperitoneally, or into the spinal canal, epinephrin in large doses causes repeated vomiting, excitement, and gen eral weakness, which may end in com plete prostration, bloody diarrhoea, and death. The findings at autopsy are characteristic. Death may be caused by cardiac or respiratory paralysis or by both. The lethal dose lies between 1 and 2 milligrammes, per kilogramme, intravenously. The subcutaneous lethal (lose lies between 5 and 6 milligrammes, the intraperitoncal between 0.5 and 0.S milligramme. S. .Amberg (Arch. In ternat. de Pharmacodyn., vol. xi, fasc. 1 and 2, 1902).
Prolonged contact of the blood with the extract does not deprive the latter of its effect on the blood-pressure. In travenous injections of adrenalin in rab bits in which the blood-vessels of one ear were deprived of the vasomotors showed a blanching of the ear of the operated side which lasted longer than that on the normal side. Following this the normal ear became perceptibly more congested than before the injec tion. This seems to show that the ex tract favors vasodilation when the cen tral nervous influence is intact; when the latter is absent, constriction results. The authors also demonstrated that sub cutaneous injection in the normal animal had no effect on the pupil and very little constricting effect on the blood-vessels, but when the sympathetic nerve was cut the pupil remained dilated for a considerable time, and vascular constriction also lasted for an equal period. S. J. and C. Meltzer (Amer. Feb. 7, 1903).