Factors A ffecting the Measurement of Absorption Bands. 129 



Table I. — Wave-length Measurements on Haemoglobin Bands. 







a-band. 







/8-band. 







Observer. 















Date. 



















CO. 



Difference. 



2 . 



CO. 



Difference. 





H. H 



5764 

 5764 

 5765 -5 

 5766 



5764 -5 

 5763 -5 

 5763 -5 



5765 -5 



5764 



5710 "5 

 5713 

 5713 -5 

 5709 

 5712 -5 

 5710 

 5711 

 5710 



5712 





5403 '5 

 5405 

 5400 

 5402 



5401 -5 

 5402 

 5402 



5402 -5 



5405 



5363 

 5357 -5 

 5361 

 5362 -5 

 5363 

 5364 

 5361 

 5360 



uoul o 



?364 









5764 -5 



5711 -1 



53 -3 



5402 '8 



5361 -5 



41 -3 



1912 



Gamgee 

 Formancli . . . 

 Dilling 

 Heubner* ... 



5790 

 5781 

 5785 

 5769 



5720 

 5710 

 5715 



70 

 71 

 70 



5438 

 5417 



5420 

 5402 



5380 

 5375 

 5378 



58 

 42 

 42 



1880 

 1901 

 1909 

 1912 



* ' Bio-chem. Ztsch.,' 1912, vol. 38, p. 345. 



the COHb by light, since it was considered inadvisable to employ any 

 screening fluid, in case this influenced the normal positions of the bands. 

 Ammonium sulphide has the property of rendering the CO compound much 

 more stable to light ; measurements done in the presence of this body gave a 

 value as high as 59 A.U. Variations were, however, still found in the 

 absolute values, in one case the wave-length varied as much as 5'4 A.U. from 

 the typical position. Alterations in the scale of the instrument were in every 

 case avoided by making the measurements from two standard lines, sodium 

 supplying that for the a-bands, the thallium line 5351 AU. for the /3-bands. 

 These differences in wave-length must be due to one of two causes, either to 

 actual differences in the wave-length of the various blood solutions measured, 

 or to retinal changes brought about by alterations in the intensity of the 

 incident light, or the previous stimuli received by the eye. Before dealing 

 with the explanation of these phenomena I will proceed with the description 

 of the second, somewhat larger, individual variation. 



Description of Individual Variation. 



Measurements of wave-length carried out by several observers on the same 

 blood solution showed that considerable divergence of opinion could exist as 

 to the apparent positions of the absorption bands. In this case also the first 



