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JAMA. 1903;XLI(25):1523-1526. doi:10.1001/jama.1903.92490440013001d.
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In 1733 Stephen Hales1 first published the idea that small arteries changed their caliber. He devised the following ingenious experiment: Tying a brass tube into the aorta of a dog and employing a head pressure equal to the normal aortic tension he injected water and measured the outflow per minute from the divided vessels of the intestines. He found that cold water diminished the flow, while hot water increased it. He also showed (by the action of drugs) that one set of agents contracted the vessels and lessened the outflow, while another set widened the vessels and increased the flow.2

The chief dominating center of the non-striped muscles of the arterial system with motor nerves (vasomotor, vasoconstrictor, vasohypertonic) lies in the medulla oblongata. The nerves which pass to the blood vessels are known as the vasomotor nerves. Without mentioning the experiments which have been made


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