The common soluble salts of barium {barium) are the chloride and the nitrate, dose, 1 grain (0.06 gm.). They are little employed except in pharmacologic laboratories and in veterinary practice. Barium has been found in the western "loco-weed" (mad-weed), which is popularly believed to be the cause of hallucinations and destruction in cows, sheep, and horses. Alsberg and Black believe it to be present in too small quantity to be responsible for the "loco" disease, and Marshall found that all the symptoms attributed to loco-weed could be accounted for by undernourishment and infections such as liver tape-worm. He further found that sheep fed with loco-weed and alfalfa kept well-nourished and showed no "loco" symptoms. Barium is therefore not the cause of the "loco" symptoms.

Barium is locally irritant and is a powerful direct stimulant of all forms of muscle. Smooth muscle may go into tonic contraction, while striped muscle shows increased contraction and a prolonged time for relaxation - the so-called veratrine action. The contraction is more deliberate than that produced through nerve stimulation. Absorption is so slow that the drug acts as a cathartic, the chloride being used for this purpose in veterinary practice. From excessive muscular contraction there may be vomiting, diarrhea, or colic. Barium sulphate is bland and has been employed to outline the alimentary tract for x-ray pictures.

Circulatory System

As the result of direct stimulation of the heart muscle, the systolic contraction is more complete and the diastolic relaxation less so, and this tendency may progress until but little blood is expelled at each systole. After death the frog's heart is firmly contracted in systole. The arterioles, including the pulmonary, cerebral, and coronary, which have no vasoconstrictor nerves, are strongly contracted from muscular stimulation; and characteristically the contraction develops more slowly and is of longer duration than arterial contraction brought about by impulses through the vasoconstrictor nervous mechanisms.

The uterus, the bladder, and other organs are also strongly contracted. There are some peculiar effects upon the central nervous system, resulting in hallucinations and other "loco" phenomena, and death is preceded by tonic and clonic convulsions. The chemic antidote in the alimentary tract is any soluble sulphate, for this forms the insoluble barium sulphate. It should be removed from the stomach by lavage or an emetic. The systemic treatment of poisoning is symptomatic, the nitrites being the best drugs to counteract the general vasoconstriction.