§ 540. Physiological Action of the Digitalins.—Whatever other physiological action this group may have, its effect on the heart’s action is so prominent and decided, that the digitalins stand as a type of heart poisons. The group of heart poisons has been much extended of late years, and has been found to include the following:—Antiarin, an arrow poison; helleborin, a glucoside contained in the hellebore family; a glucoside found in the Apocynaceæ, Thevatii neriifolia, and Thevatia iccotli; the poisonous principle of the Nerium oleander and N. odorum; the glucoside of Tanghinia venenifera; convallamarin, derived from the species of Convallaria; scillotoxin, from the squill; superbin, from the Indian lily; and the alkaloid erythrophlœin from the Erythrophlœum judiciale (see [p. 432] et seq.). This list is yearly increasing.
§ 541. Local Action.—The digitalins have an exciting or stimulating action if applied to mucous membranes—e.g., if laid upon the nasal mucous surface, sneezing is excited; if applied to the eye, there is redness of the conjunctivæ with smarting; if to the tongue, there is much irritation and a bitter taste. The leaves, the extract, and the tincture all have this directly irritating action, for they all redden and inflame mucous membranes.
§ 542. Action on the Heart.—The earlier experimenters on the influence of digitalis on the heart were Stannius and Traube. Stannius[569] experimented on cats, and found strong irregularity, and, lastly, cessation in diastole, in which state it responded no longer to stimuli. Rabbits and birds—especially those birds which lived on plants—were not so susceptible, nor were frogs.
[569] Arch. f. Physiol.
Traube[570] made his researches on dogs, using an extract, and administering doses which corresponded to from ·5 to 4·0 grms. He divided the symptoms witnessed into four stages:—
[570] Ann. d. Charité-Krankenhauses, vol. ii. p. 785.