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RESPIRATION 



is that of normal human blood diluted to i/iooth; and the 

 graduated tube gives the strength of color of the blood under 

 examination in terms of this normal standard. One defect of the 

 method was that the picrocarmine standard is not permanent, 

 and another that the color of the picrocarmine solution is not the 



same spectrally as that of the blood solution. As a consequence of 

 this both the depth and the quality of the tints of the two solutions 

 are differently affected by variations in the quality of the light at 

 the time of using the instrument. Thus if the tints agree at one time 

 of day they may be different at another ; and in ordinary artificial 

 light the results given are totally different from the results by 

 daylight. Moreover, in consequence of individual differences in 

 vision, a color match for one person is not the same as that for 

 another person, even in the same light. To remedy these defects I 

 substituted for the picrocarmine a one per cent solution of blood 

 of the average oxygen capacity of the blood of adult men (18.5 



