. The principles and practice of veterinary surgery . he vessels con-tract, therefore the movement of blood becomes more rapid inthem, as when a river entering a narrow course moves throughit with a faster stream, and that then, as the vessels widen, sothe stream becomes in the same proportion slower. But thisis far from true; the stream becomes slower as the artery orTein becomes narrowed by contraction, and then, as the tube?dUates, the stream grows faster, and then, without any appreci-able change of size, it may become slower again, till completestagnation ensues in, at least, some part of
. The principles and practice of veterinary surgery . he vessels con-tract, therefore the movement of blood becomes more rapid inthem, as when a river entering a narrow course moves throughit with a faster stream, and that then, as the vessels widen, sothe stream becomes in the same proportion slower. But thisis far from true; the stream becomes slower as the artery orTein becomes narrowed by contraction, and then, as the tube?dUates, the stream grows faster, and then, without any appreci-able change of size, it may become slower again, till completestagnation ensues in, at least, some part of the , the reader must remember that arteries are supplied withmuscular or contractile power, and when they are acted upon byany influence which causes a contraction of their muscular coat,they must, of course, become narrower, inasmuch as the muscularcells lie in rings around them. The consequence then is, thatless blood penetrates the part of the body supplied by sucharteries. The more muscular an artery is, the more lasting and. Pig. 2.—Irregular contraction of small vessels in the web of a frogs foot afterthe application of stimuli. —(Wharton Jones. ) forcible is the contraction, and the greater the obstruction ex- PHENOMENA. 9 perienced by the current of blood. In the smaller vessels thecontraction is rapidly succeeded by dilatation, which continuesfor a longer or shorter period. When an artery is reaUy inaction it gives rise to no hypersemia; on the contrary, the moreactive the vessel, the less blood will pass through it. The con-traction of the vessels is very irregular, as will be seen from thepreceding engraving (Fig. 2). If contraction of the vessel be the first change observed, it issucceeded by dilatation, and, as already stated, the stream ofblood may become faster. Then, without any change beingobserved in the size of the vessels, it becomes slower, oscillates,and finally completely stagnant, constituting stasis or passivecongestion. The contr
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Keywords: ., bookcentury1900, bookdecade1900, booksubjectveterin, bookyear1904
