The work of Bohr, Barcroft and others has shown the importance of electrolyte contents, reaction, etc., in connection with the power of hemoglobin to absorb oxygen when exposed to this gas at different pressures. Determinations of the amount absorbed at successive low pressures of oxygen give a characteristic curve which is modified by various changes in the medium in which the hemoglobin is dissolved or suspended, and it seemed possible that the comparison of such curves, made with blood in which the nature of changes in the plasma were known, with others made from normal blood might give a clue as to the abnormality of the plasma. There are many other directions in which such determinations might be useful.
Barcroft's instrument allows a direct comparison between the amount of oxygen absorbed by a cubic centimeter of blood at a low oxygen pressure with that absorbed at the point of saturation.
MacCALLUM WG. AN APPARATUS FOR THE STUDY OF THE DISSOCIATION OF OXYHEMOGLOBIN. JAMA. 1917;LXIX(7):523-524. doi:10.1001/jama.1917.02590340023007