The acquisition of oxygen by the blood in the lung 207 



devising a fresh method of experiment, or on the other hand that his 

 doing so was of the nature of a challenge. 



Hartridge's method is based on the fact that the substitution of 

 CO for O 2 in haemoglobin is associated with a movement of the bands 

 towards the violet end of the spectrum. 



Hartridge claims that in mixtures of the two the degree of 

 movement of the band is a measure of the relative amount of CO 

 haemoglobin present. Hartridge's spectroscope has two slits ; when 

 you look into it you see two spectra, one immediately above the 

 other but these spectra present this difference, that the blue end of 

 the uppermost one is to the right of the field, the blue end of the 



A 



\ 



, \ 

 1 \ 



I \ 



, 3. 







'/, 



,< I. 



FIG. 100. The method of formation and adjustment of the reversed spectra. A shows 

 the ordinary arrangement with single slit. B shows the arrangement with double slit. 

 C, the bands of O 2 Hb as they would appear in the spectroscope. D, the a bands have 

 been adjusted into line. E, the oxygen has been replaced by CO, and the a bands 

 have shifted away from one another. F, the lower spectrum has been displaced by 

 the micrometer, so that the a bands are again in line. 



lower one to the left. One of the spectra is " reversed." Suppose C 

 in the figure to be the two spectra. Let us fix our attention on the 

 sharper and narrower of the two haemoglobin bands the one nearer 

 the red end. By a movement of a lever attached to the instrument 

 the upper spectrum may be shifted in the field of vision till the 

 two a bands are exactly one above the other (D). If now the 

 oxyhaemoglobin be replaced by a CO haemoglobin the a bands 

 will no longer appear to be one above the other, but as in E. The 

 final operation is to make them coincide once more as in F. This is 

 accomplished as I have said by moving a lever on the side of the 

 apparatus the arc through which it is moved is read off on the 



