Volume 2

The respiratory function of the blood / by Joseph Barcroft.

  • Barcroft, Joseph, 1872-1947.
Date:
1925-1928
Catalogue details

Licence: Attribution-NonCommercial 4.0 International (CC BY-NC 4.0)

Credit: The respiratory function of the blood / by Joseph Barcroft. Source: Wellcome Collection.

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    so I shall pause for a moment to consider it. Imagine the curve drawn on a sheet of india-rubber, which could be stretched hori¬ zontally without alteration in its vertical dimensions; then the altera¬ tion in the curve which would be caused by rise of temperature could be simulated by mere stretching of the sheet. This relationship is excellently shown in the series of curves given by A. Y. Hill and Brown (3) for blood at different temperatures. They are as it were all the same curve but drawn on different horizontal scales. The property is such as would be caused by a simple alteration in the equilibrium constant of the reaction, without any alteration in such factors as are responsible for the degree of inflection of the curves. Therefore we at once get at a conception which separates causes which define the curve into two categories, those which are responsible for the equilibrium constant and for the degree of inflection respectively. A particular factor may affect both the constant and the inflection but it need not necessarily do so and temperature appears to affect the former without altering the latter. The effect of temperature will, however, be treated in greater detail in a future chapter. The effect of salts. Concerning the effect of salts on the oxygen dis¬ sociation curve we know very little. Among the earliest observations made by Camis and myself (4) was the one that certain salts added to a solution of haemoglobin in distilled water altered the curve, making it more inflected. I never know whether it was more fortunate or unfor¬ tunate that the observation was made at so early a stage; it was unfor¬ tunate because at that time the effect of hydrogen-ion concentration was not appreciated and therefore not controlled and it is certain that many of the salts used, e.g. sodium phosphate, altered the hydrogen- ion concentration of the fluid. Moreover, the distilled-water solution was not itself so free from salts as it would have been, had the investigation been made a year later. The fortunate circumstance, however, was that had the discovery not been made at the time it was, it might have been long postponed; for the whole effect of salts on the dissociation curve might have been attributed to changes in hydrogen-ion concentration. In any case the thing must be done again and it wants doing both in relation to the hydrogen-ion con¬ centration and the haemoglobin concentration. We are only waiting for a certain base line from which to start, in order to test the effect of salts on dilute solutions of haemoglobin. So far as may be gathered from the work on the velocity constants carried out by Hartridge and Houghton (5) salts have no effect on the rate at which really dilute