DAVID L. DRABKIN 



precise tool of spectrophotometry 5 , with the hope that it would permit 

 us to speak about these functional entities in more exact and satis- 

 factory terms. By suitable extensions in the optical method 6 " 10 , we 

 have secured quantitative information upon certain details, not possible 

 or not attainable with equal accuracy by other techniques. And occa- 

 sionally we have been doubly repaid by the measurements themselves 

 in the disclosure of new facts. 



Biological position of oxygen — Though in this new world the slogan 

 ' need for energy ', even in the affairs of the cell, has replaced that of 

 • need for oxygen ', the stature of this gas has not shrunk. Oxygen 

 ' spark-plugs ' the oxidative, energy-yielding processes in aerobic 

 organsisms and tissues. The use of oxygen creates the need, and the 

 familiar formula of ' balance of demand and supply ' applies in the 

 concept of oxygen homeostasis, which remains of imperative import- 

 ance. It may be said without hesitation that oxygen homeostasis is one 

 of the most beautiful examples in biological economy of the balanced 

 integration of a number of complicated separate processes. Particularly 

 striking, from the biochemical viewpoint, in this integrated activity are 

 the intracellular agents (' respiratory chemicals '), so similar and yet 

 so different, and each apparently so suitable functionally, as haemo- 

 globin in the erythrocytes, poised to resist oxidation and to favour 

 oxygenation, and cytochrome c in tissues, poised to favour oxidation 11 . 



I shall confine myself to two of several aspects which have recently 

 claimed our attention, in the respective phases of ' supply ' and 

 ' demand ', of the broad problem of oxygen homeostasis : 1 the col- 

 lection of data required for the construction of an oxygen dissociation 

 curve which would reflect conditions in the arterial blood of man 

 in vivo, and 2 the study of cytochrome c metabolism, which suggests 

 that oxygen consumption is under hormonal control, operative through 

 its effect on the concentration in tissues of the haemin protein. 



OXYGEN DISSOCIATION OF ARTERIAL BLOOD IN VIVO 



It appears particularly appropriate that the first presentation of our 

 work upon the establishment of the oxygen dissociation curve of the 

 arterial blood of man in vivo should be made at the Conference in 

 honour of Barcroft, who pioneered this very field 12 and long maintained 

 an interest in it 13 . These experiments were a collaborative effort with 

 C. J. Lambertsen and P. L. Bunce. My share was to furnish the data 

 on the percentage of oxyhaemoglobin in the samples. I was happy to 

 leave in the capable hands of Lambertsen and Bunce what seemed to 

 me the major job of accurately determining the corresponding oxygen 

 tensions. 



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