§ 120. =Action on Warm-Blooded Animals.=--If a sufficient quantity of a solution of a potassic salt is injected into the blood-vessels of an animal, there is almost immediate death from arrest of the heart’s action. Smaller doses, subcutaneously applied, produce slowing of the pulse, dyspnœa, and convulsions, ending in death. Small doses produce a transitory diminution of the force of arterial pressure, which quickly passes, and the blood-pressure rises. There is at first, for a few seconds, increase in the number of pulsations, but later a remarkable slowing of the pulse. The rise in the blood-pressure occurs even after section of the spinal cord. Somewhat larger doses cause rapid lowering of the blood-pressure, and apparent cessation of the heart’s action; but if the thorax be then opened, the heart is seen to be contracting regularly, making some 120-160 rhythmic movements in the minute. If the respiration be now artificially maintained, and suitable pressure made on the walls of the chest, so as to empty the heart of blood, the blood-pressure quickly rises, and natural respiration may follow. An animal which lay thirty-six minutes apparently dead was in this way brought to life again (_Böhm_). The action of the salts of potassium on the blood is the same as that of sodium salts. The blood is coloured a brighter red, and the form of the corpuscles changed; they become shrivelled through loss of water. Voluntary muscle loses quickly its contractility when a solution of potash is injected into its vessels. Nerves also, when treated with a 1 per cent. solution of potassic chloride, become inexcitable. § 121. =Elimination.=--The potassium salts appear to leave the body through the kidneys, but are excreted much more slowly than the corresponding sodium salts. Thus, after injection of 4 grms. of potassic chloride--in the first sixteen hours ·748 grm. of KCl was excreted in the urine, and in the following twenty-four hours 2·677 grms. § 122. =Nitrate of Potash= (KNO₃).--Pure potassic nitrate crystallises in large anhydrous hexagonal prisms with dihedral summits; it does not absorb water, and does not deliquesce. Its fusing point is about 340°; when melted it forms a transparent liquid, and loses a little of its oxygen, but this is for the most part retained by the liquid given off when the salt solidifies. At a red-heat it evolves oxygen, and is reduced first to nitrite; if the heat is continued, potassic oxide remains. The specific gravity of the fused salt is 2·06. It is not very soluble in cold water, 100 parts dissolving only 26 at 15·6°; but boiling water dissolves it freely, 100 parts dissolving 240 of the salt.