The physiology of the circulation in plants : in the lower animals, and in man : being a course of lectures delivered at surgeons' hall to the president, fellows, etc of the Royal college of surgeons of Edinburgh, in the summer of 1872 . c valves as they exist in man, it is desirable that you shouldbe acquainted with the relations, structure, and functions of themore rudimentary valves found in the veins of mammals, and inthe hearts of the lower 1 VMe Memoir On the Valves of the Vascular System in Vertebrata, bythe Author. Transactions Royal Society of Edinburgh, vol. xxiii. part iii
The physiology of the circulation in plants : in the lower animals, and in man : being a course of lectures delivered at surgeons' hall to the president, fellows, etc of the Royal college of surgeons of Edinburgh, in the summer of 1872 . c valves as they exist in man, it is desirable that you shouldbe acquainted with the relations, structure, and functions of themore rudimentary valves found in the veins of mammals, and inthe hearts of the lower 1 VMe Memoir On the Valves of the Vascular System in Vertebrata, bythe Author. Transactions Royal Society of Edinburgh, vol. xxiii. part iii.,1864. The preparations on which this investigation is based are preserved inthe Hunterian Museum of tbe Royal College of Surgeons of London. 200 DR J. BELL PETTIGEEW ON THE Venous Valves—their Structure, etc.—The valves of the veinsvary as regards the number of the segments composing them. In thesmallest veins, and where small veins enter larger ones, one segmentonly is present. In the middle-sized veins of the extremities twosegments are usually met with ; while in the larger veins, as theinternal jugulars of the horse, three and evenfour segments are byno means uncommon. (Fig. 131, a, b, c, d, e, f, g, h, i, j.) Fig. Fig. 131.—A, External jugular vein of horse inverted. Shows valve, consisting of three(r, s, t) segments. — Original. B.—Section of external jugular vein of horse. Shows valve, consisting of two segments(a, b), with dilatations (g, h) corresponding to the sinuses of Valsalva, in the arteries.—Original. 0.—External jugular vein of horse opened, to show the relations of the segments (a, />),where they come together (e), and are united by fibrous tissue, (r). The free margin of oneof the segments is seen at e, the attached margin at a.— Original. D.—Portion of femoral vein distended with plaster of Paris. Shows dilatations (h, g) inthe vessel behind the valve; a, b, segments of valve; e, point where the segments come to-gether when the v
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