This section is from the book "Materia Medica And Therapeutics Inorganic Substances", by Charles D. F. Phillips. Also available from Amazon: Materia medica and therapeutics.
In a frog, if strong solutions be injected near the cardiac region, the heart is suddenly arrested in diastole, but under a slower distal absorption this does not occur, nor is there evidence of the specific paralyzing effect upon the heart contended for by Eulenburg. On the contrary, the heart has been found beating one or two hours after complete paralysis of the nervous system and of respiration (Damourette, Saison). The heart-action is rendered slower, but, as a rule, the capillaries are narrowed before this slowing. It is not the soaking through of the cardiac muscles by bromide of potash that produces these effects (as it does in the experiments on the frog mentioned above), but the gradual lowering of the spinal reflex irritability. The observers just named, as well as Meuriot, Hammond, and Amory, have witnessed the narrowing of vessels in the web, the tongue, or the brain of frogs or dogs; but others have failed to see this, and Dr. H. C. Wood considers the present proof insufficient; neither does the observation that divided capillaries of a bromin-ized frog bleed less than normal ones seem free from criticism, for he suggests that lowered heart-action would account for lessened bleeding. But, these observations apart, I think the surface-pallor that follows the use of bromides, and the lessening of secretion and discharge, point strongly in the same direction (narrowing of vessels). There is also post-mortem evidence of lessened blood in capillaries when influenced by bromide (Saison), and we may quote, too, the clinical fact that bromides relieve many forms of capillary congestion, especially cerebral and uterine, whereas in patients with cerebral anaemia the effects are often distressing. Thus, while Dr. Wood considers capillary contraction to be "somewhat probable," I hold it to be more clearly ascertained.
That the heart-action and the general circulation are slowed in the lower animals is also evident from many experiments (Damourette and
Pelvet, loc. cit., and Schouten: Schmidt's Jahrbuch, Bd. cliv, p. 11). This is more marked with the potassium salt than with the others, and may be largely credited to the alkali; the bromide of sodium has comparatively slight effect in this direction (Eulenburg, Rabuteau). In man, the depressing effect of any bromides on the circulation is not constant. Pletzer noticed it (Schmidt, August, 1868), and Bartholow records a depression of 10 to 20 beats per minute after a dose of 2 dr.; but Dr. Bill, Dr. Voisin, Dr. Russell Reynolds, and others have failed to observe such a result with doses of 20 gr. and upwards, continued for some time. It is evident that circulatory depression is a less constant and characteristic effect of the bromides than nerve-sedation.