A text-book of physiology, for medical students and physicians . een mm. and mm. per sec. * Von Kries, Archiv f. Physiologie, 1887, 279; also Abeles, ibid., 1892, Burton-Opitz, Am. Journal of Physiology, vols. 7 and 9, and PflugersArchiv, vols. 123 and 124, 1908. 470 CIRCULATION OF BLOOD AND LYMPH. Vierordt reports some interesting calculations upon the velocity of theblood, in the capillaries of his own eye. Under suitable conditions,* themovements of the corpuscles in the retina may be perceived in consequenceof the shadows that they tlirow upon the rods and cones. The visual im
A text-book of physiology, for medical students and physicians . een mm. and mm. per sec. * Von Kries, Archiv f. Physiologie, 1887, 279; also Abeles, ibid., 1892, Burton-Opitz, Am. Journal of Physiology, vols. 7 and 9, and PflugersArchiv, vols. 123 and 124, 1908. 470 CIRCULATION OF BLOOD AND LYMPH. Vierordt reports some interesting calculations upon the velocity of theblood, in the capillaries of his own eye. Under suitable conditions,* themovements of the corpuscles in the retina may be perceived in consequenceof the shadows that they tlirow upon the rods and cones. The visual imagesthus produced may be projected upon a surface at a known distance from theeye and the space traversed in a given time may be observed. The distanceactually covered upon the retina may then be calculated by the following con-struction, in which A-B = the distance traveled by the projected image;., the distance of the surface from the eye; and a-n, the distance of theretina from the nodal pointof the eye. We have thenthe proportion ab : an :: AB X AB: An, or ab = According to this method,Vierordt calculated that thevelocity of the blood in thehuman capillaries is equal toabout to mm. persecond. In the arteries, more- , , . Fig. 185.—Diagram of the eve to show the con- OVer, It may be Observed struction used to determine the size of the retinal 4-V.^i- 4-U„ _ _ i j. image when the size of the external object is known: that the average Velocity n, The nodal point of the eye. See text. diminishes the farther one goes from the heart,—that is, the smaller the artery,—andreaches its minimum when the arteries pass into the , Volkmann reports for the horse the following figures: Ca-rotid, 300 mms.; maxillary, 232; metatarsal, 56 rams. In the veinsalso the same fact holds. The smaller the vein—that is, the nearerit is to the capillary region—the smaller is its velocity, the maxi-
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