The heart in vaso-motor paresis and paralysis is weakened in the first instance by the direct action of the poison on the medulla oblongata and the intracardiac ganglia. Its pulsations, at first retarded in frequency, become accelerated soon after the introduction of the poison, the pulse rate increasing rapidly and the waves becoming smaller and more easily compressible in proportion to the frequency of the pulse, which generally counts from 100 to 120 and more per minute at a comparatively early stage of the poisoning process. But an equally potent cause of heart failure is its depletion by the simultaneous stagnation of the blood mass in the veins of the abdomen. Finally, to complete the mischief, we have not only anæmia of the semi-paralytic oblongata, but the scanty blood supply this important centre receives becomes also surcharged with carbonic acid. Oxyhæmaglobin disappears almost entirely from the blood under the circumstances detailed, as both pulmonary and internal respiration are greatly interfered with, the blood tending more and more towards that thin dark condition which it presents after death, and which has been taken as _prima facie_ evidence of the direct blood-poisoning action of snake virus by one and all of previous investigators. That under the powerful combination of causes, each of which is in itself sufficient to endanger life, and greatly intensified as paresis gradually deepens into paralysis, the heart, even of large animals, succumbs in a comparatively short time, may be readily understood. The _blood-pressure_, under the circumstances just detailed, must necessarily be _nil_. Observations by means of the sphygmograph at the bedside of a person suffering from snake-poison are scarcely feasible, except, perhaps, in a hospital, and thus far are not on record. We must, therefore, once more fall back on Feoktistow's experiments, which show that even the smallest doses (0.02 to 0.04 mllgr.) of the dried poison _per kilo_ injected into the vein of a cat caused a fall in the blood-pressure almost immediately, without influencing either pulse or respiration, but that two to four mgr. were sufficient to reduce the blood-pressure to zero and bring on collapse, infusions of blood only raising it temporarily. Of drugs raising the blood-pressure he found ammonia the most effective, but only after slight doses of the poison; after lethal ones it had no effect whatever on the blood pressure but greatly increased the hæmorrhagic process in all internal organs. This important observation should be kept in mind by those who inject ammonia in serious snakebite cases, and it probably applies likewise to _the excessive use of alcohol_.