Poiseuille was the first after Stephen Hales to make any important addition to the knowledge of the physiology of circulation. In his graduation thesis, above, he described a “hemodynamometer” invented by himself and which he used to repeat some of Hales’s blood-pressure experiments. With his hemomanometer, a mercury manometer, which was a great improvement on the long tube used by Hales, Poiseuille showed that the blood-pressure rises and falls on expiration and inspiration, and measured the degree of arterial dilatation produced by each heart beat. English translation in Edinb. med. surg. J., 1829, 32, 28-38. See also his paper in J. Physiol. exp. path., 1828, 8, 272-305. Digital facsimile from the Internet Archive at this link.