METH^MOGLOBIN. 113 



lines. It is not so distinct as are the two lines and the 

 solution may have to be strengthened to make it plainly 

 visible. The j;wo lines reappear upon shaking the solu- 

 tion with air, the oxyhaemoglobin being formed again. 



METH^EMOGLOBIN. 



In its percentage composition methaemoglobin differs 

 very little, if any, from oxyhaemoglobin, and probably is 

 formed by a rearrangement of the atoms in the oxyhaemo- 

 globin molecule. It is produced whenever oxyhaemoglobin 

 is dried in the air at ordinary temperatures or when it is 

 acted upon by weak acids. Certain oxidizing agents also 

 will convert oxyhaemoglobin into metha3moglobin. It is 

 also found in transudations and cystic fluids which con- 

 tain blood; moreover in the urine during hgematuria and 

 haemoglobinuria, as well as in the blood itself in certain 

 cases of poisoning or after a large destruction of blood- 

 corpuscles by burns of the skin. 



In the methasmoglobin molecule the oxygen is more 

 firmly attached than in oxyhaemoglobin,, being removable 

 neither by a vacuum nor by another gas. Like oxyhaemo- 

 globin, however, it is changed by weak acids or alkalies 

 into haematin and an albuminous substance. Like oxy- 

 haemoglobin, too, it is converted by reducing agents or by 

 putrefaction, where reducing forces are at work, back into 

 hemoglobin. 



Methasmoglobin crystallizes in brownish-red needles 

 or sometimes in plates. It is easily soluble in water, giv- 

 ing a brown solution, which becomes red on the addition 

 of an alkali. The spectrum of the alkaline methaemoglobin 

 solution has two bands much similar to those of oxyhaemo- 

 globin, one on the D line, the other near the E line. 



