PROTEINS 121 



venient consisting in comparing blood or diluted blood with a 

 scale giving reds of different intensities corresponding to definite 

 concentrations of hemoglobin. 



Derivatives of the Hemoglobins. Carbon Monoxide-Hemo- 

 globin. Hemoglobin forms compounds with various gases other 

 than oxygen such as carbon monoxide, carbon dioxide, etc. Car- 

 bon monoxide, which is a constituent of illuminating gas com- 

 bines with hemoglobin in molecular proportions. Its union ap- 

 parently is firmer than that of oxygen, and apparently it com- 

 bines with hemoglobin at the same place as does oxygen, for if 

 both gases are present, carbon monoxide hemoglobin is formed, 

 and the taking up of oxygen is interfered with. The carbon 

 monoxide may be removed, however, by passing a stream of 

 air through the liquid for some time, and oxyhemoglobin will be 

 formed. In cases of asphyxiation by illuminating gas, carbon 

 monoxide is found in the blood, thus preventing the proper 

 transportation of oxygen to the tissues. 



Solutions of carbon monoxide hemoglobin are a bright cherry 

 red. The absorption bands look much like those of oxyhemo- 

 globin, two dark bands between the D and the E lines. They 

 are slightly nearer the violet end of the spectrum however, and 

 on adding Stokes' reagent to the mixture they do not, as does 

 the hemoglobin spectrum, give place to a single broad band. 



Carbon dioxide apparently combines with hemoglobin at a 

 point different from that at which oxygen combines, as combin- 

 ing with one does not prevent hemoglobin from combining with 

 the other also. 



Mefhemoglobin. Methemoglobin is a compound derived from 

 oxyhemoglobin. It contains the same amount of oxygen as oxy- 

 hemoglobin, but the oxygen is more firmly united than in oxy- 

 hemoglobin. Methemoglobin is found in the blood after poison- 

 ing with chlorates, amyl nitrite, etc., and is found occasionally 

 in the urine, in transudates, cystic fluids, and elsewhere. Out- 

 side the body it may be prepared for study by adding fresh 

 potassium ferricyanide solution, permanganate or other sub- 

 stances to oxyhemoglobin solutions. The solution turns a muddy 



