226 METH^MOGLOBIN. 



Hiifner l have been most generally used for physiological purposes, 

 but there are many other forms. 2 The value of A. has been deter- 

 mined by several observers for haemoglobin, 8 oxy -haemoglobin, 4 carbon- 

 monoxide haemoglobin 8 and methaemoglobin, 6 for certain fixed parts 

 of the spectrum; as also its value for bile and urinary pigments. 7 If 

 the value of A. has been determined for two substances in two differ- 

 ent parts of the spectrum, the amount of each substance in a mixture 

 of the two may be determined spectrophotometrically. 8 This is a 

 possibility of considerable importance when working with blood in 

 which varying amounts of haemoglobin and oxy-haeinoglobin may 

 occur simultaneously. 



6. Methsemoglobin. When blood or solutions of haemo- 

 globin which have been exposed to the air for some time are 

 examined with the spectroscope they are frequently found to 

 exhibit, in addition to the more or less persistent absorption 

 bands of oxy-hsemoglobin, a marked band of absorption between 

 C and D, closely resembling but differing slightly in position 

 from the band which hsematin shows in acid solution (see below). 

 This band may also frequently be observed in many pathological 

 fluids, such as those from ovarial cysts, etc., which are coloured 

 by blood, and in urine when similarly coloured. 9 The substance 

 to which the band is due is known as niethsemoglobin. 10 It may 

 be readily prepared in the laboratory by the action of many 

 reagents such as acids or alkalis, or more conveniently of certain 

 salts, on solutions of oxy-hsemoglobin. Of these salts those which 

 may perhaps on the whole be most advantageously employed to 

 obtain the spectrum of methsemoglobin are nitrites, 11 potassium 

 ferricyanide, or potassium permanganate. 12 With the two latter 

 salts the spectrum of methsemoglobin may be obtained as follows. 

 To 10 c.c. of a moderately strong solution of oxy-haamoglobin 

 add a few drops of a dilute ('5 1*0 p.c.) solution of either of the 

 salts and warm very gently. If on examination with a spectro- 

 scope the two bands of oxy-hsemoglobin are still strongly visible, 



i Jn. f. prakt. Chem. N.F. Bd. xvi. (1877), S. 290. Cf. Otto, Pfltiger's Arch. 

 Bd. xxxvi. (1885), S. 12. Glazebrook has constructed a modification of Hiifner's 

 instrument. See Lea, Jl. of Physiol. Vol. v. (1883), p. 239. 



' 2 For all details of instruments and spectrophotometry in general see G. u. H. 

 Kriiss, Kolonm. u. quant. Spektralanal. 1891, Very complete details are given in 

 Neubauer u. Vogel, Analyse d. Hams, 1891, S. 411. 



3 Hiifner, Zt.f. physiol. Chem. Bd. in. (1879), S. 7. 



4 Hiifner, Ibid. Bde. i. (1878), S. 317, in. (1879), S. 4. Von Noorden, Ibid. 

 Bd. iv. S. 9. Otto, Ibid. Bd. vn. S. 62. Pfliiger's Arch. Bd xxxi. (1883), S. 244. 

 xxxvi. (1885), S. 12. Sczelkow, Ibid. Bd. XLI. (1887), S. 373. 



5 Marshall, Zt. f. physiol. Chem. Bd. vn. (1882), S. 81. 



6 Otto, Pfliiger's Arch. Bd. xxxi. (1883), S. 263. 



7 See Vierordt, loc. cit. or G. u. H. Kriiss, loc. cit. 



8 Vierordt, loc. cit. 



9 Hoppe-Seyler, Zt. f. physiol. Chem. Bd. v. (1881), S. 6. 



10 The name was first used by Hoppe-Seyler in 1865, Centralb. f. d. me.d. W/xs. 

 S. 65. But see also previously Ibid. 1864, S. 834, and Virchow's Arch. Bd. xxix. 

 (1864), Sn. 233, u. 597. 



11 Gamgee, Phil. Trans. 1868, p. 589. 



12 Jaderholm, Zt. f. Biol. Bd. xin. (1877), S. 193. 



