NOTE ON THE RELATIONSHIP BETWEEN BARO- 



METRIC PRESSURE AND CARBON-DIOXIDE 



EXCRETION IN MAN 



Higley's application of the product-moment correlation method 

 to the question o£ the influence of barometric pressure on carbon- 

 dioxide excretion in man^ seems to deserve some extension. For- 

 tunately, this is possible on his published data. 



Instead of inquiring merely whether there is a correlation be- 

 tween barometric pressure and carbon-dioxide excretion, one may 

 profitably consider (a) whether the volumes excreted by the same 

 individual at different periods in the day are correlated, and (b) 

 whether the amounts excreted by different individuals on the same 

 day are correlated. 



The correlation between the volumes respired by the same indi- 

 vidual at different times of Observation on the same day might be 

 due either to internal physiological conditions,^ or to Variation f rom 

 day to day in external conditions (barometric pressure, or some 

 other environmental factor). A correlation between the volumes 

 excreted by different individuals on the same day would necessarily 

 be due to some common external condition. 



Designating Higley's subjects by a^ b and c, and the three Ob- 

 servation periods by m^^morning, w = noon and ^=evening, I 

 find the following results.^ 



A. For correlations between different Observation periods for 

 the same individual: 



For a, 



rmn = + 0.30 ±0.12, rme= — O.I5=bO.I3, rne = -|- 0.00 ± O.I3 



1 Higley : Biochemical Bulletin, 1913, ii, p. 393. 



2 These might conceivably tend to bring about either a positive or a nega- 

 tive correlation. 



3 In determining the correlations, the means and Standard deviations were 

 necessarily recalculated for each product-moment, since several observations 

 are wanting. Thus N varies from coefficient to coefficient. 



530 



