A textbook of human physiology / translated from [the] 6th German edition by W. Stirling.

  • Landois, Leonard
Date:
1888
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Licence: Public Domain Mark

Credit: A textbook of human physiology / translated from [the] 6th German edition by W. Stirling. Source: Wellcome Collection.

Provider: This material has been provided by Royal College of Physicians, London. The original may be consulted at Royal College of Physicians, London.

    95/980 page 43
    THE BLOOD GASES. minimal amount, and does not exceed what distilled water at the temperature of the body would take up at the partial pressure of the 0 in the air of the lungs {Lo'fhar Meyer). {/>) A/most the total 0 of the hlood is chemically united, and therefore not subject to the law of absorption. It is loose/// united to the h;Bmoglobin of the red corpuscles, with which it forms oocyheemogloUn (§ 15). With regard to the taking up of O, the total quantity of blood behaves exactly like a solution of haemoglobin free from O {Preyer). The absorption of O is more rapid in blood than in a solution of Hb. The absorption of this quantity of 0 is completely independent of pressure; lience, animals confined in a closed space, until they are nearly asphy.xiated, can use up almost all the 0 from the surrounding atmosphere. The fact of the union being independent of pressure is ]iroved by the following ;—The blood only gives off copiously its chemically united 0 -when the atmo- spheric pressure is lowered to 20 millimetres, Hg ()Vorvi Miillcr); and, conversely, blood only takes up a little more 0 when the pressure is increased to 6 atmospheres {Bert). Physical Methods of obtaining 0 from Blood.—Notwithstanding the chemical union between the Hb and O, all the O of the blood can be expelled from its state of combination by those means which set free absorbed gases—{<i) by introducing blood into a Torricellian vacuum ; {/j) by boiling ; (c) by the conduction of other gases [H, N, CO, or NO] through the blood, because the oxyhsemoglobin compound is so loose that it is decomposed even by these physical means. Reducing Reagents.—Amongst chemical reagents the following reducing substances—ammonium sulphide, suli>huretted hj'drogen, alkaline solutions of sub- salts or Stokes's fluid, iron filings, &c., rob blood of its O (§ 15). Halation to Fe.—The amountof iron in the blood (0-55 in 1000 parts) stands in direct relation to the amount of lib ; this to tlie quantity of blood-corpuscles ; and this, in turn, to the specific gravit}' of the blood. The amount of 0 in the blood, therefore, is nearly proportional to the specific giavity of the blood, and it is also in proportion to the amount of iron in the blood. Picard affirms that 2'36 grams of iron in the blood can fix chemically 1 gram 0 ; while, according to Hoppe-Seyler, the proportion is 1 atom iron to 2 atoms 0. During mori)hia narcosis the amount of 0 in the blood is diminished (JEtcald); after hsemor- rhage the arterial blood is saturated with 0 {J. G. Ott). Disappearance of 0 in Shed Blood.—Even immediately after blood is shed, there is a slight disappearance of 0, as a physiological index of respiration of the tissues within the living blood itself (§ 132). When blood is kept long outside of the blood-vessels, the quantity of 0 gradually diminishes, and if it be kept for a length of time at a high temperature it may tlisapjtear altogether. This depends u2ion decomposition occurring in the blood, whereby reducing sub- stances are formed which consume the 0. All kinds of blood, however, do not act with ei]ual energy in consuming 0, e.g., venous blood from active muscles acts most energetically, while that from the hepatic vein has very little effect. CO., appears in the blood in place of tlie 0, and the colour darkens. The amount of CO.j produced is sometimes greater than that of the 0 consumed. Eelation to Acids.—If blood (or a solution of oxyhrenioglobin) be acted upon by adds {e.g., tartaric acid) until it is strongly acid, 0 can be pumped out in consideraldy less amount, while the formation of CO.^ is not increased. \Vc must, therefore, assume that, during the decomposi- tion of the Hb caused by the acids (§ 18), a decomposition product becomes more highly oxidised by the intense chemical union of the 0 at the moment of its origin {Lothar Meyer, Zuntz, Strasshurg). The same phenomenon occurs when oxyhajmoglobin is decomposed by boiling. 37. IS OZONE PRESENT IN BLOOD ?—On account of the numerous and energetic oxidations which occur in connection with the blood, the question has often been raised as to whether the O of the blood exists in the form of ozone (O3). Ozone, however, is contained neither in the blood itself (Sehonheii/) nor in the blood-gases obtained from it. Nevertheless, the red corpuscles (and Hb) have a distinct relation to ozone. (1) Tests for Ozone. — Hremoglobin acts as a conveyer of ozone, i.e., it is able to remove the active 0 of other bodies and to convey or tran.sfer it at once to other easily oxidisable substances. {a) Turpentine which has been exposed to the air for a long time always contains ozone. The tests for the latter are starch and potassium iodide, the ozone decomposing the iodide, when the iodine strikes a blue with the starch, {b) Freshly-prepared tincture of guaiacum is also rendered
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