156 



Scientific Proceedings (54). 



photometer. When this has been done with a solution of pure 

 oxyhemoglobin of known concentration in an absorption tube of 

 known length k can then be calculated. After the value of k has 

 been determined for pure oxyhemoglobin from human blood the 

 concentration of hemoglobin in laked human blood can be derived 

 from a measurement of I' /I. Oxyhemoglobin from ox blood may 

 be conveniently substituted for human hemoblogin in the deter- 

 mination of k since it was shown in Tubingen that the constant has 

 the same value for both hemoglobins. In the present study 

 homogeneous light was not employed, but the measurements were 

 made in a very narrow interval in the spectrum (about 4 mm)- 

 This is not accompanied by an appreciable error as long as the 

 concentration and linear thickness are kept within narrow limits. 

 The measurements were always made in two regions in the spec- 

 trum, (1) at the maximum in green of the second absorption band 

 of oxyhemoglobin, and (2) at the minimum in yellowish green 

 between the two absorption bands of oxyhemoglobin. The reason 

 for this follows on combining the two equations for these measure- 

 ments. If Ii = Iie~ hlc represent the conditions in the first 

 region and I 2 ' = l2e~ kilc those in the second region, one would 

 have after logarithmating and dividing, 



remains constant independent of concentration and linear thick- 

 ness. If 



logy-, 



= ?= K. 



(2) 



Therefore 



varies then some other substance with constants different from ki 



