258 Mr. A. Cbmpton. Optimum Temperature of an 



In women, as at sea-level, the values are about 11 per cent, lower than for 

 men, but greater irregularity is observed. 



Graphic representations and tables of the results are given. To render 

 possible a complete survey of the alveolar gas pressures and the haemoglobin 

 percentages recorded for acclimatised persons at varying atmospheric pressures 

 and heights above sea-level, the values previously published* are included in 

 the graphs. 



In conclusion, I wish to express my cordial appreciation of the kind help 

 and hospitality received during the investigation. My thanks are specially 

 due to Dr. Mary Lapham, of Highlands, Dr. Stokes and Mr. J. Tull, of 

 Waynesville, and to Dr. George Purefoy and Messrs. Taylor and Johnstone 

 (U.S. Weather Bureau), of Asheville. 



My sincere thanks are also due to Dr. J. S. Haldane for his advice and for 

 the loan of standardised instruments, and to Prof. Yandell Henderson, of 

 Yale University, for the further loan of apparatus. 



Constancy of the Optimum Temperature of an Enzyme under 

 Varying Concentrations of Substrate and of Enzyme. 

 By Arthur Compton, Imperial Cancer Eesearch Fund. 



(Communicated by Sir J. E. Bradford, K.C.M.G., Sec. R.S. Beceived 

 June 10— Read June 25, 1914.) 



In a recent paperf a new enzymic relation is recorded. For the enzymic 

 hydrolysis of salicin — by the enzyme which Gabriel Bertrand and the author^ 

 have named salicinase — it is found that, in an action of fixed duration,§ the 

 temperature of greatest activity of the ferment is always the same, whatever 

 the dilutions of substrate and of enzyme adopted for the determination. In 

 other words, the duration of the action being constant, the optimum tem- 

 perature of the ferment is independent of the concentration both of the 

 substrate and of the enzyme. The observation is suggestive : if true of one 

 enzyme it may be true of all, and possibly becomes the enunciation of a 

 general law. Herein, for the moment, lies its main interest. 

 * ' Phil. Trans.,' B, vol. 203, pp. 351-371. 



t Arthur Compton, ' Roy. Soc. Proc.,' B, vol. 87, p. 245 (1914). 



X Gabriel Bertrand and A. Compton, 'Comptes Eendus,' vol. 157, p. 797 (1913). 



§ For the variation of the optimum temperature of an enzyme with the duration 

 of the enzyme action, see Gabriel Bertrand and A. Compton, ' Comptes Rend us,' 

 vol. 152, p. 1518 (1911) ; 'Ann. Inst. Past.,' vol. 26, p. 161 (1912). 



