THE SPECIFICITY OF HEMOGLOBIN 



41 



days were too rough for the task of settling the matter. The merest 

 glance with the Hartridge reversion spectroscope, which shows the 

 relative positions of the point of maximum density of the bands, 

 demonstrates the difference between the spectrum of Planorbis blood 

 and that of, say, human blood. Twenty-five Angstrom units are quite 

 a large disparity with an instrument which will work to about two 

 Angstrom units. So far as my own observations go, Sorby was not 

 very wide of the mark. 



But Sorby's results lay forgotten, and the question was raised again 

 by Vies (6), in 1922, who carefully mapped out the spectra of a number 

 of animals, notably Arenicola and the horse, finding quite con- 

 siderable differences. 



My own attention was attracted to the matter at the Physiological 

 Congress at Edinburgh in 1923. Wishing to demonstrate a Uttle 

 apparatus for the equilibration of small quantities of blood, I thought 

 it would form a striking demonstration to make some observations 

 with it on the blood of the earthworm. At once, in the Hartridge 

 spectroscope, I saw that the bands were differently placed from those 

 of human haemoglobin, and also, that they were displaced to a less 

 degree by treatment with carbon monoxide. 



Even now work has only commenced on the subject of the exact 

 positions of the spectral bands throughout the animal kingdom ; but 

 the following table gives the positions of the a-band of Jiaemoglobin 

 for a number of animals relatively to that for man (7). The table 

 also gives data for the a-band of oxy haemoglobin and of CO -haemo- 

 globin. 



