This section is from the book "A Text-Book Of Pharmacology, Therapeutics And Materia Medica", by T. Lauder Brunton. Also available from Amazon: A text-book of pharmacology, therapeutics and materia medica.
[Stimulation is shown by the direct application of the drug to the heart, stopping its spontaneous pulsations completely, while it still contracts on the application of a stimulus either mechanical or electrical.]
[Depression or paralysis is shown by stimulation, not only of the vagus trunk, but of the venous sinus itself, having lost all power to slow or stop the heart; and by the direct application of muscarine also having no action.]
Vagus-ends in the Heart.
[Stimulation either of the ends of the vagus in the heart or of the inhibitory ganglia is shown by the injection of a drug rendering the pulse slow after previous division of the trunks of the vagi.]
It is said to render the peripheral ends of the vagus more sensitive, so that a slighter stimulus will stop the heart applied to the trunk.
[Depression or paralysis is shown by irritation of the vagus trunk no longer producing slowness or stoppage of the pulsations of the heart, while the application of muscarine, or irritation of the venous sinus, will still cause stoppage.]
[Stimulation is evidenced by slowing of the pulse, disappearing on section of the vagi.]
Increased blood-pressure. Venous blood. Ammonia (in frogs). Carbonic oxide. Chloroform. Chloral hydrate. Butyl-chloral. Belladonna (atropine). Hyoscyamus (hyoscyamine). Stramonium (daturine). Aconite (aconitine). Veratrum viride (veratroidine). Tobacco (nicotine). Digitalis (digitalin). Hydrocyanic acid.
[Depression is evidenced by a quick pulse, which is not rendered slow by irritation of sensory nerves which usually produce slowing of the pulse, e.g. the central end of one vagus.]
Diminished blood-pressure and substances which produce it, e.g. nitrite of amyl and other nitrites.
Large doses of such substances as stimulate it in small doses, vide adjoining list.