194 



THE BLOOD 



the attempt must also be made to convert the oxyhemoglobin into hemoglobin and 

 the latter into the former. Thus, if a certain solution yields the a- and /3-bands, 

 a reducing agent should be added to obtain the y-band, because this conversion 

 establishes the presence of blood with much greater certainty than the presence 

 of the first two bands alone. Quite similarly, a solution in which hemoglobin has 

 been proved to exist spectroscopically, should be oxidized by shaking it until the 

 7-band is eventually displaced by the two bands of oxyhemoglobin. 



Solutions of carbon monoxid hemoglobin also give two absorption bands 

 which may be mistaken at times for those produced by oxyhemoglobin ; however, 

 a differentiation is readily possible if the solutions are properly diluted. When this 

 has been done, the superposition of the different spectra so far described, will show 

 that the bands of carbon monoxid hemoglobin are situated somewhat nearer the 

 blue end of the spectrum; and besides, they are permanent in character, i.e., 

 they cannot be fused into a single one by the addition of a reducing agent. 



Fig. 108. — The spectra of oxyhemoglobin in different grades of concentration, of 

 reduced hemoglobin, and of carbonic oxid hemoglobin. (After Preyer and Ganger.) 

 1 to 4. Solution of oxyhemoglobin containing: (1) less than .01 per cent., (2) .09 per 

 cent., (3) .37 per cent., (4) .8 per cent. 5. Solution of (reduced) hemoglobin containing 

 about .2 per cent. 6. Solution of carbonic oxid hemoglobin. In each case of the six 

 cases the layer brought before the spectroscope was 1 cm. in thickness. The letters 

 indicate Fraunhofer lines and the figures wave-lengths expressed in H 00.00 millimeter. 



Nitric oxid hemoglobin shows two absorption bands which are paler and less 

 distinct than those of carbon monoxid hemoglobin and furthermore, their charac- 

 teristics cannot be altered by reducing agents. 



The absorption bands of methemoglobin in watery or acidified solutions are very 

 similar to those of acid hematin, which body gives three to four distinct bands. 

 A differentiation, however, can easily be effected, because methemoglobin when 

 mixed with a small quantity of an alkali and a reducing agent, shows the absorp ion 

 band of reduced hemoglobin, while under precisely the same conditions hematin 

 exhibits the spectrum of an alkaline hemochromogen solution. In alkaline 

 solutions this substance shows three bands, two of which are similar to those of 

 hemoglobin. ' They differ from the latter in that the j8-band is more conspicuous 

 than the a-band ; moreover, the latter occurs in relation with a third band which is 

 fainter and occupies a position somewhat to the left of the D-line. 



