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.
The important experiments of Blake, so far as they can be practically applied, would point to a marked difference between the action of proto- and per-salts on the blood and the circulation. Injecting 10 gr. of protosulphate (in solution) into the jugular vein of a dog, there occurred a quick but temporary depression of the heart-action and blood-pressure; with 28 gr. heart-action stopped, and pressure fell to zero; 70 gr., in divided doses, caused a gradual general dulness, and death from asthenia - the right cavities of the heart were distended with dark blood, the left contained 1 oz. of brighter color, but the coagulating power was lost.
When 2 gr. of persulphate, dissolved in 2 oz. of water, were injected into the same vessel, pressure was diminished for a brief time, but quickly rose again when 3 gr. more were given; death soon followed; the left heart-cavities were empty and contracted, the right distended, the blood coagulated at once when exposed; the lungs were bright scarlet and contracted, and Dr. Blake attributed death to contraction of their capillaries preventing the supply of arterial blood to the left heart. Five grains thrown into the axillary artery raised the blood-pressure at once from 6 to 12 degrees (by the haemadynamometer); death followed, and both sides of the heart contained dark blood, implying that the lung-contraction was overcome in this instance, but only by an extreme degree of pressure. The obstruction of the lung-capillaries might be caused by a physical change in the blood, rather than by contraction of the vessels, but the quantity seems too small for the former effect, and an analogous contraction of vessels is produced by digitalis, which proves its possibility.
The general results of the experiments go to demonstrate that proto-salts lower cardiac irritability, and in toxic doses arrest heart-action, cause slow respiration, sedation of nerve-system, and death by depression: per-salts, on the other hand, have no direct action on the heart, certainly do not lessen its irritability; they cause symptoms of pressure on the nerve-centres, and death through interference with the pulmonary circulation, cutting off the supply to the left heart. Collaterally, it is argued that proto-salts cannot be readily oxidized in the blood, or else some "peroxide-effects" would be developed from 70 gr. of a proto-salt; and that per-salts are not readily reduced, or the effects of such small quantities would not be so persistent (Journal of Anatomy and Physiology, 1869), but reviewing all the experiments and conclusions, we must doubt whether the mechanical forcing of substances into the blood-current can be held to compare with natural absorption and assimilation. The difference, however, exerted by the two classes of salts upon coagulation, has an important bearing upon their use for local injections, on the formation and solution of clot, on embolism, etc.