202 



PEACTICAL PHYSIOLOGY 



amyl nitrite, 1 there is formed a certain amount of methaemoglobin 

 and a certain amount of nitric oxide haemoglobin. The combination 

 of the two gives a spectrum very similar to simple methaemoglobin 

 (Spectrum 17 in Chart). 



stB C 



75J 70| 65 60| 

 k B C D 



55 



50 



45 



G 



FIG. 146. Absorption-spectra. 



12, Methaemoglobin (strong solution) ; 13 and 14, Methaemoglobin (weak solutions) ; 

 15, Methaemoglobin (alkaline solution); 16, Nitric oxide haemoglobin; 17, Mixttare of 

 Methaemoglobin and nitric oxide haemoglobin. 



If the product of the action of nitrites be treated with ammonium 

 sulphide, the spectrum passes through a transient oxy haemoglobin 

 stage, succeeded by reduced haemoglobin, and later becomes nitric 

 oxide haemoglobin. 



5. The visible Spectrum of Acid-haematin. If some diluted de 

 fibrinated blood be treated with a little glacial acetic acid and gently 

 warmed, it will assume a dark brown colour. If it be diluted suffi- 



1 Care must be taken to avoid excess of amyl nitrite, or so-called photo-met- 

 haemoglobin, characterised by one broad band between D and E, will be formed. 



