Elements of human physiology / by L. Hermann ; translated from the sixth edition by Arthur Gamgee.

  • Gamgee Arthur, 1841-1909.
Date:
1878
Catalogue details

Licence: Public Domain Mark

Credit: Elements of human physiology / by L. Hermann ; translated from the sixth edition by Arthur Gamgee. Source: Wellcome Collection.

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

    88/620 (page 68)
    The special features of the process described above, and which renders it preferable to others employed for the same purpose, are (1) the blood may readily be brought directly, without previous defibrination, from the blood- vessels into the apparatus where its gases are separated; (2) the blood is at once introduced into a very large vacuous space, so that the O-pressure outside the blood is always very much below the dissociation tension of the 0 of the blood, and the latter therefore escapes very rapidly ; (3) tlie A'acuum is kept in a dry condition by the sulphuric acid in the drying-chamber ; this appears to have very great influence in facilitating the escape of gases from the blood. Having separated and collected the total gases given off by a known volume or weight of blood, these are measured and analyzed.] In order to determine whether gases are in a state of simple solution or of loose chemical combination in the blood, either absorption experiments must be made under different pressures, with blood which has been freed from gases, or determination of tension must be made. The methods for effecting the latter, which are of special imi3ortance in reference to the chemistry of respira- tion, will be given in Chapter IV. 1. Oxygen gas is found in arterial blood, on an average, in the proportion of 16*9 volumes per cent, (the gas being calculated under a pressure of 1 metre and 0° C) (Pfliiger)' : the amount of oxygen in venous blood varies greatly (Chapter IV.); in venous blood from muscles in a state of rest the amount was found to be only 5*96 volumes per cent., taking an average of five determina- tions. The deportment of blood, which has had its gases removed, towards oxygen, shows that the latter is not merely absorbed by the blood, hid J or the most part chemically combined luith it. The amount (by weight) of the oxygen taken up by blood is almost entirely independent of pressure, and does not therefore follow Dalton's law. But if the blood corpuscles are removed, and simple blood plasma be taken, or (since the latter is difficult to obtain, and immediately coagulates, whilst as regards combination with 0 the fibrin-formers may be considered as unimportant), instead of plasma, plain serum (page 64), be agitated with oxygen, the gas is merely absorbed (L. Meyer), It follows from this that the oxygen of the blood is chemically combined with a substance contained m the blood corpuscles, but is only absorbed by the plasma or serum (that is, by the water they contain, for serum absorbs just so much oxygen as pure distilled water ^). This pro- position must likewise be applied to the oxygen normally present in the blood. Hsemoglobin is the substance which forms the loose chemical 1 Pfluger,' Die normalen Gasmensre des arteriellen Blutes nach verbesserten Methoden.' Centralhlatt f. d. med. Wissenschaft, 1867, No. 46. 2 It has been stated (Fernet) that plain serum likewise taices up a certain amount of oxygen, independently of pressure ; this result is probably owing to the presence of a slight amount of ha;moglobin in the serum. Pfliiger (Archiv, vol. i. p. 73.) found 100 vols, of dog's serum to contain the following gases :— Oxygen 0-2 vols, at 0° C and 1 metre. Free carbonic acid . . . 26-8 „ „ „ Combined carbonic acid . . 7*1 „ „ „ Nitrogen ... • 17 ,f » » 35-8 vols.