Relation between Alkalosis and Tetany. 229 



posed increases in the oxygen saturation of the blood at definite 

 oxygen tensions. Wilson, Stearns and Thurlow used Barcroft's 2 

 formula 



y Kx n 

 100 1 — Kx n 



in which y is the percentage saturation of the blood with oxygen, 

 x is the oxygen tension in millimeters of mercury, and n is a con- 

 stant to which Barcroft assigned the value 2.5 for human blood. 

 Wilson, Stearns and Thurlow assumed the same value for dog 

 blood although calculations from Barcroft's value for dog blood 

 (Barcroft, page 50) show that, in this case, the value of n was not 

 2.5, but approximately 2.2. Barcroft worked at 40 mm. C0 2 , 

 Wilson, Stearns and Thurlow at o mm. C0 2 . According to Bar- 

 croft, this difference does not affect the value of n in human blood. 

 But calculating from the figures of Wilson, Stearns and Thurlow, 

 which differ considerably from one another, the value of n is 

 found to be not 2.5, nor 2.2, but approximately 1.5. Using this 

 value of n in recalculating the value of K from the data of Wilson, 

 Stearns and Thurlow it is found that this is not regularly greater 

 in the blood of parathyroidectomized dogs than in the blood of 

 normal dogs. The significance of such changes in percentage 

 oxygen saturation as do occur is obscure. Many factors, other 

 than change in reaction or in alkaline reserve may be responsible. 

 Barcroft's figures (Barcroft, page 62) indicate a specific effect of 

 phosphates in increasing the value of K and decreasing that of n. 

 Moreover, any unrecognized decrease in n will increase the ap- 

 parent value of K. A few calculations indicate that the retention 

 of phosphate and acumulation thereof in the blood after parathy- 

 roidectomy may possibly be sufficient to account for any observed 

 changes in percentage oxygen saturation without involving any 

 change in reaction or in alkaline reserve. Hastings and Murray 3 

 have shown by their own work and by reference to the more 

 recent literature that there is no direct evidence of either an in- 

 creased alkalinity nor increased C0 2 -capacity after parathyroid- 

 ectomy. 



* Barcroft, J., "The Respiratory Function of the Blood," Cambridge, 1914- 

 8 Hastings, A. B. and Murray, H. A., Jr., Journal of Biological Chemistry, 1921, 

 xlvi, 233. 



