GENERAL PROPERTIES: THE CORPUSCLES. 



433 



trum with two absorption bands closely resembling in posi- 

 tion and appearance those of oxyhemoglobin. They are dis- 

 tinguished from the 

 oxyhemoglol^in bands 

 by being slightly 

 nearer the blue end 

 of the spectrum, as 

 may be demonstrated 

 by observing the wave 

 lengths or, more con- 

 veniently, by super- 

 posing the tw^o spectra. 

 Moreover, solutions of 

 carbon monoxid hem- 

 oglobin are not re- 

 duced to hemoglobin 

 by adding Stokes's 

 liquid, two bands be- 

 ing still seen after such 

 treatment. A solu- 

 tion of carbon mon- 

 oxid hemoglobin suit- 

 able for spectroscopic 

 examination may be 

 prepared easily by 

 passing ordinary coal- 

 gas through a dilute oxyhemoglobin solution 

 and then filtering. 



Derivative Compounds of Hemoglobin. — There are a number 

 of pigmentary bodies which are formed directly from hemoglobin 

 by decompositions or chemical reactions of various kinds. Some 

 of these derivative substances occur normally in the body. The 

 best known are as follows * : 



Methemoglobin. — When blood or a solution of oxyhemoglobin 

 is allowed to stand for a long time exposed to the air it undergoes 

 a change in color, taking on a brownish tint. This change is due to 

 the formation of methemoglobin, and it is said that to some extent 

 the transition occurs very soon after the blood is exposed to the air, 

 and that, therefore, determinations of the quantity of hemoglobin 

 by the ordinary colorimetric methods should be made promptly to 

 avoid a deterioration in color value. Methemoglobin may be 

 obtained rapidly by the action of various reagents on the blood, 



* For more detailed information concerning the chemistry and Hterature 

 ©f these compounds, see Hammarsten, "Physiological Chemistry," translated 

 by Mandel; Abderhalden, "Lehrbuch d. physiolog. Chemie," 1914. 



aBC 



Fig. 185. — Diagram to show the variations in the ab- 

 sorption spectrum of reduced hemoglobin with vary- 

 ing concentrations of the solution (after Rolletf). The 

 numbers to the right give the strength of the hemo- 

 globin solution in percentages; the letters give the posi- 

 tions of the Fraunhofer lines. For further directions 

 as to the use of the diagram, see the description of Fig. 

 IS-i 



for a few minutes 



