. Biology of the vertebrates : a comparative study of man and his animal allies. Vertebrates; Vertebrates -- Anatomy; Anatomy, Comparative. hitermil J ransportation 347 Capillaries*--!.! ^^~ Unlike the twigs of a tree that come to an end, capillaries are con- tinuous and keep right on, forming anastomosing networks which have a larger total carrying capacity than the blood vessels they immediately connect (Fig. 282). The result is that the rate of flow of the blood stream slows down as it goes through the capillary networks, just as a swiftly flowing river that spreads out upon entering a lake
. Biology of the vertebrates : a comparative study of man and his animal allies. Vertebrates; Vertebrates -- Anatomy; Anatomy, Comparative. hitermil J ransportation 347 Capillaries*--!.! ^^~ Unlike the twigs of a tree that come to an end, capillaries are con- tinuous and keep right on, forming anastomosing networks which have a larger total carrying capacity than the blood vessels they immediately connect (Fig. 282). The result is that the rate of flow of the blood stream slows down as it goes through the capillary networks, just as a swiftly flowing river that spreads out upon entering a lake loses iis momentum. Blood cells in capillaries may be said to "crawl," but as the size of the blood vessels. Circular Muscle Fibers Fig. 282. A terminal arteriole, surrounded by a "stopcock" cuff of circular muscle fibers, which is supplied by a nerve ending for regu- lating the flow of the blood. The capillary they are passing through enlarges, network having greater internal expanse than they "hustle" more and more. the arteriole shows why the blood flows T -ii • i r more slowly thrpugh the capillaries than in In capillaries the rate of move- w . , ,A(; F .., x the arterioles. (Alter Keith.) ment, which varies within wide limits, has been given as one twentieth of an inch per second, while in the highway of the aorta it is three hundred times as rapid. Capillaries may measures from mm. to mm. in diameter, while the largest human arteries and veins sometimes attain a diameter of. Please note that these images are extracted from scanned page images that may have been digitally enhanced for readability - coloration and appearance of these illustrations may not perfectly resemble the original Walter, Herbert Eugene, b. 1867; Sayles, Leonard Perkins, 1902-. New York : Macmillan Co.
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