Physiology and biochemistry in modern medicine (1918) (14594445760)

Identifier: physiologybioche00macl (find matches)

Title: Physiology and biochemistry in modern medicine

Year: 1918 (1910s)

Authors: Macleod, John James Rickard, 1876-1935 Pearce, R. G. (Roy Gentry), 1884-

Subjects: Physiology Biochemistry

Publisher: St. Louis : Mosby

Contributing Library: Columbia University Libraries

Digitizing Sponsor: Open Knowledge Commons

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theaorta it will close the semilunar valves and force its way under pressureinto the coronary vessels, subsequently escaping by the coronary sinus into •the right auricle. Very soon after the perfusion is started the heartbegins to beat vigorously and regularly, thus offering a suitable prepara-tion upon which to test the first three mentioned conditions necessaryfor the nutrition of the cardiac musculature (Fig. 39). If the temperature of the solution is allowed to fall considerably, thebeat becomes much slower, and if the cooling is proceeded with, the heartwill after a while cease beating altogether. If the pressure is lowered,the beat will not necessarily become slower but very much feebler, andwill soon cease. In general it may be said that the temperature of thesolution affects the rate of the beat, and the pressure affects its strength. THE NUTRITION F THE HEART 1G3 Funnel (refilling& air vent) StocK solution(Diluted blood+a salt solution) Metal panHot water bath

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Fig. 39.—One form of apparatus for recording tracings from an excised heart (Langendorffmethod). The heart is kept warm by a water bath (heart warmer), and the perfusion fluid isalso warmed. The driving pressure in this apparatus is supplied by gravity. (From Jackson.) Ifi4 THE CIRCULATION OF THE BLOOD It is, however, obvious that in perfused preparations changes in pres-sure are likely to cause alterations in rate as well as in force, unlessgreat care is taken to keep the heart itself as warm as the perfusionfluid. The importance of an adequate pressure in the coronary vessels hasbeen clearly brought out in certain experiments in which the heat hasbeen maintained for a short time by establishing a pressure in the cor-onary vessels by means of indifferent fluids or gases. Thus, if oxygengas is allowed to pass through the vessels under pressure, the heart willbeat for a short time, and the same result has been observed even Avhenmineral oil or mercury has been perfused under pressure

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1918

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