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.
Very small doses give a characteristic markedly acid taste, and lessen the sensation of thirst; 10 to 15 min. of the dilute acid, administered several times at intervals, stimulate the appetite and exert some astringent effect on the gastric and other secretions. If continued, however, the medicine induces dyspepsia with acid eructation; colic, and even diarrhoea, which may be due to the large amount of alkaline sulphates formed, as well as to direct irritation.
The local symptoms induced by toxic doses of the strong acid are very severe; intensely acid pungent taste is followed by acute burning pain in the mouth, pharynx, and stomach, and violent retching and vomiting, the ejecta usually containing dark blood; there is extreme thirst and great sense of distress - sometimes purging with tenesmus. The faucial inflammation may induce suffocation, angina, or laryngeal oedema, and thus prove fatal early in the case, or peritonitis may be set up, and if death do not occur from collapse, it may follow on perforation of the oesophagus, stomach, or bowel in twelve to forty-eight hours after the poisonous dose; should life be saved for the time, the inflammation of the alimentary-tract is likely to be followed by serious contraction, etc.- swellings, and suppuration of the parotid glands may occur. Any slough produced by this acid is black in color.
Bobrick found, with frogs, that this acid, given by the stomach, or applied to the skin, caused the heart to act more slowly, and finally stopped it in diastole. Hertwig, experimenting on mammalia, found that moderate doses of the dilute acid lowered the pulse-rate and the temperature, while arterial tension was increased. I am not aware that similar results have been verified on the healthy human subject, nor has proof been given of the acid's power to lower temperature in febrile conditions. It has been said by some that the blood becomes less, by others more, coagulable, but its exact state is not ascertained; nor do we rightly know whether the smaller vessels are contracted or not by the acid (Nothnagel; v. p. 228). When injected into the veins it causes instant death from coagulation of blood and thrombosis, and the corpuscles are altered or destroyed by toxic doses taken internally.
In cases of poisoning by the acid, the disturbance of circulation is mainly secondary to the gastric irritation: there may be faintings, passing on to actual syncope or collapse, the pulse becoming later rapid and small, the extremities icy cold, and respiration labored and superficial.