File:A text-book of comparative physiology for students and practitioners of comparative (veterinary) medicine (1890) (14740388876).jpg

Identifier: textbookofcompar00mill (find matches)
Title: A text-book of comparative physiology for students and practitioners of comparative (veterinary) medicine
Year: 1890 (1890s)
Authors: Mills, Wesley, 1847-1915
Subjects: Physiology, Comparative
Publisher: New York, London, D. Appleton and company
Contributing Library: Columbia University Libraries
Digitizing Sponsor: Open Knowledge Commons

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h gradually diminishingtoward the capillaries, in which it would be feeble; lower stillin the smaller veins; and at its minimum where the great veinsenter the heart. Actual experiments confirm the truth of theseviews; and, as the subject is one of considerable importance, weshall direct attention to the methods of estimating and record-ing an animals blood-pressure. First of all, the well-known fact that, when an artery is cut,the issuing stream spurts a certain distance, as when a water-main, fed from an elevated reservoir, bursts, or a hjTdrant isopened, is itself a proof of the existence of blood-pressure, andis a crude measure of the amount of the pressure. One of the simplest and most impressive ways of demon-strating blood-pressure is to connect the carotid, femoral, orother large artery of an animal by means of a small glass tube(drawn out in a peculiar manner to favor insertion and reten-tion by ligature in the vessel), known as a cannula, by rubber 228 COMPARATIVE PHYSIOLOGY.
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Fig. 197. THE CIRCULATION OB THE BLOOD. 229 Fi«. 19?.—Apparatus used in making a blood-pressure experiment (after Foster) //. b.pressure-bottle, elevated so as to raise the pressure several inches of mercury, asseen in the manometer (m) below. It contains a saturated solution of sodium car-bonate; r. t, rubber tube connecting the pb with the leaden tube: /. t, tube madeof lead, so as to be pliable, yet have rigid walls; t«. c, a stop-cock, the top of whichis removable, to allow escape of bubbles of air; p, the pen, writing on the roll ofpaper, r. The former floats on the mercury; m, the manometer, the shaded por-tion of the bent tube denoting the mercury, the rest is tilled with a fluid unfavor-able to the coagulation of the Dlood, and derived from the pressure-bottle; ca, thecarotid, in which is placed the cannula, and below the latter a forceps, which maybe removed when the blood-pressure is to be actually measured. The registrationof the height, variation, etc., of blood-pressu

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