Arsenic (As = 74.4) is a metal usually found in combination with cobalt, tin, and copper ores.

Pharmacodynamics.

Central Nervous System. - Peripheral neuritis and secondary cord degeneration in chronic poisoning. In other cases there are "no certain indications of direct action."

Muscular System. - Secondary fatty degeneration.

Respiration slackens in toxic doses from low blood-pressure.

Heart weakens in toxic doses from direct action.

Blood-pressure falls in toxic doses from direct action on muscle coat of arterioles, especially of the splanchnic area.

Alimentary Tract. - Arsenic produces an irritation of the mucosa, extreme dilatation of the intestinal capillaries, and a specific fatty degeneration of the gastro-intestinal epithelium.

Secretory Glands. - Little affected.

Pharmacodynamics (continued).

Metabolism. - Arsenic produces a stimulation of the blood-forming organs; reduces the relative alkalinity of the blood; inhibits the glycogenic function of the liver; and produces a tendency to fatty degeneration of the epithelium of the intestine and of the lung alveoli, of the liver, kidney, muscle-cells of the heart and blood-vessels, and of striated muscle.

Temperature is sometimes elevated because of the inflamed mucosa.

Absorption is fairly rapid from mucosa under favorable conditions.

Excretion. - Arsenic is excreted chiefly by the kidneys, but elimination is slow, as it forms nuclein compounds in the tissues.

Local Action. - Irritant and escharotic if skin be broken.

Tolerance to the oral ingestion of arsenic is acquirable, presumably because the intestines no longer absorb it.

Symptoms.

Medicinal Doses.

No symptoms; if bagging under eyes appears, drug should be discontinued for a while.

Acute Poisoning. Dysphagia; gastric pain. Abdominal distress; colic. Vomiting; serous diarrhea. Giddiness, headache, cramps. Pallor.

Weak, feeble pulse. Sighing respiration. Collapse; coma. Death in 24 to 96 hours.

Chronic Poisoning. 1st Stage: Weakness and lassitude. Bagging under eyes. Lachrymation. Anorexia. Nausea; possibly vomiting. Gastric discomfort.

2d Stage:

Catarrh of eyes, nose, and throat Jaundice; hepatic swelling. Exanthems; desquamation. Melanosis and herpes.

3d Stage:

Persistent headache. Acute localized pains. Formication of extremities. Erythromelalgia; myalgia. Sensory peripheral neuritis. Motor neuritis of extensors of extremities. Symmetrical atrophy. Mental apathy.

Therapeutics.

Arsenic is almost specific in chorea minor, is helpful in some forms of skin diseases, and has wrought striking cures in trypanosomiasis and in chronic syphilis.

Dosage.

Arseni Trioxidum, 0.001 to 0.005 Gm. Liquor Potassii Arsenitis, 0.05 to 0.5 mil. Arsphenamin or Salvarsan (paradiamidodioxyarsenobenzolum hydrochloride) contains 35% Arsenic, 0.6 Gm.