Externally and Locally. - Potassium bromide is slightly sedative to mucous membranes when applied locally, lessening the reflex irritability, particularly of the pharynx.

Internally. - Digestive System. - Locally on the mouth and stomach it produces increased salivation and irritation, as a result of its salty taste. Excessive doses have occasioned a sense of coldness in the epigastrium, with nausea and looseness of the bowels.

Circulatory System. - Potassium bromide depresses the circulation, causing the pulse to become slower, softer, and weaker, and shortening the systole while prolonging the diastole of the heart. The caliber of the vessels is diminished, although arterial pressure is lowered. The potassium ion is responsible for the cardiac depression. It is not present in the other bromide salts.

Nervous System. - Potassium bromide acts as a depressant to the cerebrum. It causes a retardation of the flow of ideas and somnolence. The functions of the motor areas are also depressed. This action on the cerebrum is believed to be due to the bromine ion. The sleep caused is of a dull and heavy character, not refreshing, and is not induced in the presence of pain, or great mental anxiety, or grief. On the medulla there is no marked action.

Spinal Cord. - Potassium bromide diminishes the reflex excitability of the spinal cord. This with its action on the motor centers causes marked depression in muscular activity. There is also a marked diminution, under large and continued dosage, in the activity of the sexual function, and the muscular power of the bladder is somewhat impaired. Anesthesia of the bladder, joints, skin, and mucous surfaces is a constant symptom of prolonged administration.

Respiratory System. - Under full doses the respirations are slower and shallower, owing to slight depression of the respiratory center, paralysis of which may cause death, although fatal paralysis may affect the heart because of the poisonous influence of the potassium ion upon the cardiac muscle.

Absorption and Elimination. - The bromides are very rapidly absorbed, and begin to be eliminated quickly, chiefly by the kidneys (increasing the flow of urine), and also by the skin, saliva, intestinal and mammary glands, and the bronchial mucous membrane. The sulphur nitrogen and chlorides in the urine are increased and the amount of phosphates decreased.

Notwithstanding the rapid elimination of the bromides, under prolonged administration they tend to accumulate in the system, being found abundantly in all parts of the body, particularly in the blood. Nerve-structures contain small amounts. The drug is often found in the urine several weeks after stopping its administration. It has been thought that the bromides were able to replace the chlorides in the tissues to a certain extent. This deduction has been made the basis of an important hypothesis for the treatment of epilepsy - to be considered later.

Temperature. - Immoderate doses cause a reduction of temperature, due to depression of the circulation and lessening of tissue-change.

Eye. - There may occur dilatation of the pupil, conjunctival catarrh, diplopia, amblyopia, dimness of vision, and dilatation of the retinal blood-vessels.

Uterus. - A diminution of the catamenia may sometimes be present.

Untoward Action. - The susceptibility of individuals to the untoward action of the bromides is extremely variable. The symptoms observed are - gastric uneasiness with eructation, nausea and vomiting, analgesia of the epiglottis and pharynx, bronchial catarrh, hoarseness and cough, acute coryza and conjunctivitis, offensive breath, dysuria, diminished sensibility of the genito-urinary mucous membrane, and a variety of cutaneous eruptions.

Poisoning. - Bromism, as the symptoms of poisoning are termed, may be divided into an acute and a chronic form.

Acute Bromism, resulting from a single toxic dose, is manifested by violent frontal headache, great muscular weakness, incoordination of movements, abolition of reflexes, somnolence, slow and shallow breathing, subnormal temperature, lusterless eyes, and very slow and weak pulse, death usually extremely rare, resulting from either respiratory or cardiac failure. Death has resulted from 2 1/2 ounces (75 Gm.) taken in a period of forty-eight hours. Treatment of acute bromism is best effected by salt solution by hy-podermoclysis, enteroclysis, or infusion.

Chronic Bromism, caused by prolonged use of the bromides, is characterized by mental apathy, constant drowsiness, hallucinations, depression, considerable cutaneous anesthesia, muscular weakness, poor circulation, cold extremities, marked anemia, impairment of the sexual function, deranged digestion, and cutaneous eruptions of various forms collectively designated as "bromine acne." Its continued use over years may result in permanent mental impairment.

Treatment of Poisoning. - The drug should be immediately withdrawn and methods adopted to hasten elimination, such as the administration of diuretics, cathartics, etc. Tonics, such as strychnine, iron, and the cardiac stimulants, should be given, while exercise and change of scene may counteract the psychical symptoms.

It is claimed that the daily administration of Fowler's solution causes a rapid disappearance of bromine eruption.

Comparative Action of the Bromides. - Potassium bromide 15 contains 66 per cent. of bromine. It is the most toxic to the heart and muscular system.

Sodium bromide, 78 per cent. of bromine, is less hypnotic, as the sodium ion is known to increase cerebral activity, but the Na ion being indifferent to heart and muscle, it is less toxic.

Ammonium bromide, containing the NH3 ion, shows slight cardiac stimulation, but is otherwise identical with the potassium salt.

Lithium bromide is the richest in bromine, containing 92 per cent., and is probably the most hypnotic of all. Its action more nearly resembles that of the sodium salt.