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Sur la force du Cceur Aortique (1828) ; RechercJies sur les causes du 

 Mouvement du Sang dans les veines (1830) ; and in 1839 Mou-c. dans 

 les vaisseaux capillaires. It is in this quarto work, with four plates, 

 that he figures and describes his hoenivdynamometer, which is essentially 

 a mercury manometer connected with the interior of an artery by 

 means of a lead tube filled with a solution of carbonate of potash. 

 He watched the oscillations of the mercury in the open limb of the 

 tube. Ludwig added a float, and had the genius to cause this float 

 to write on a recording cylinder, and thus at one coup gave us his 

 kymograph, or wave-writer, and the application of the graphic method 

 to physiology. Poiseuille's fourth work, on the flow of fluids in 

 capillary tubes, was published in 1847. 



" Influence of respiration on the motion of the blood in the arteries. Poiseuille 

 perceived, by means of his instrument, what Haller and Magendie had already 

 observed, namely, that the strength of the blood's impulse is increased during expira- 

 tion ; in which act the chest is contracted, and the large vessels in consequence com- 

 pressed. The column of mercury in his instrument rose somewhat at each expiration, 

 and fell during inspiration. M. Poiseuille found that the rise and fall of the mercury 

 is the same in arteries the distance of which from the heart is different, and that in 

 ordinary tranquil respiration it amounts to from four to ten lines. The increase of the 

 blood's impulse by expiration is in many persons so great, that the pulse at the radial 

 artery becomes imperceptible when inspiration is long continued, and the breath held. 

 This is the case with myself, and in some measure explains the fable of persons possessing 

 the power of altering the action of their hearts at will." (Miiller's PhysioL, I. p. 221.) 



" Poiseuille also measured the degree of dilatation of an artery at each pulse beat. 

 He laid bare the carotid of a horse for about 3 decimetres 12 inches -and inclosed this 

 part of the artery in a tin box, which he Riled with water, placing in the upper wall of 

 the box a glass tube. At every pulsation the water rose 70 millimetres and fell again 

 the same distance during each pause. He calculated that the artery was dilated to 

 about -1% of its capacity at each beat." 



IN connection with the doctrine of " reflex action " we cannot 

 pass over the name of MAESHALL HALL (1790-1857), who 

 was born near Nottingham studied at Edinburgh (1809- 

 1812, M.D.). He began practice in Nottingham in 1817, but went 

 to London in 1826, where he practised for seven-and-twenty years 

 with great success. He published various papers on the circulation 

 of the blood and on blood-letting. His chief work, however, is in 

 connection with reflex action, Tlie Reflex Function of the Medulla 

 Oblongata and Medulla Spinalis (Phil. Trans., 1833), which attracted 

 the attention of J. Miiller and was published in his Archiv. 

 His paper on the True Spinal Marrow and the Excito-motor System 

 of Nerves was not inserted in the Transactions. His New Memoirs 

 on the Nervous System were published in 1843. He was an 

 indefatigable worker in many branches, and his name still remains 

 associated with the " Marshall Ha\l method " of restoring suspended 



