CHAP. II.] THE BLOOD. HI 



in which the oxygen has become irremovable by a vacuum, but which 

 is decomposed at once by reducing agents, which first liberate oxy-haemo- 

 globin and subsequently form reduced haemoglobin. This view has 

 lately received the support of Jaderholm. 



Taking all the facts in consideration we must admit that under the 

 innuence of various agents the loosely combined oxygen of haemoglobin 

 becomes irremovable by CO, and by a vacuum, whilst the new compound 

 still preserves the crystalline form of oxy-haemoglobin, and the capability 

 of being recrystallized. In this condition the body, which appears per- 

 fectly stable, can again be made to furnish haemoglobin. It is certainly 

 convenient at present to retain for this body the term Methaemoglobin. 



Hoppe-Seyler, who was the first 1 to describe briefly and to name 

 methaemoglobm, long ago arrived at the conclusion that probably no 

 definite body, such as is implied by the possession of a special name, exists, 

 but that it represents an intermediate stage in the decomposition of 

 haemoglobin into haematin and a proteid 8 . 



FIGURE 23. 



Spectrum 1. (Preyer, PI. 2, sp. 9.) Haematin in alkaline solution. 

 A single absorption band between C and D, from wave-length 618 to wave- 

 length 587. Strong absorption of the blue end 



Spectrum 2. (Preyer, PL 2, sp. 10.) The same as 1, but more concen- 

 trated. As the concentration of the solution increases the band extends 

 more towards the red than the green. The red end of the spectrum is 

 much absorbed. 



Spectrum 3. (Preyer, PI. 1, sp. 11.) Haemochromogen in alkaline 

 solution (Stokes' reduced haematin). The spectrum is distinguished from 

 all others by the extraordinary intensity and sharpness of the absorption 

 band nearest to D. This extends from wave-length 567 to 547. The 

 second absorption band, which is very much less intense and has less sharply 

 defined borders, extends from about wave-length 532 to 518. The solution, 

 even when concentrated, absorbs very little of the red. Violet and blue 

 are strongly absorbed. 



Spectrum 4. Methaemoglobin. In weak solutions of certain strengths 

 four absorption bands may be made out. In a strong solution one is seen, 

 the centre of which, according to the Author's measurements, corresponds 

 to wave-length 632. According to Preyer this band would be a little nearer 

 to C, the centre corresponding to wave-length 634. 



Spectrum 5. Diluted blood treated with acetic acid. An absorption 

 band in the red, the centre of which corresponds to wave-length 640. 

 According to Preyer the centre of this band corresponds to 65 6' 6. 



Spectrum 6. Spectrum of acid haematin dissolved in ether. The 

 position of the three bands between B and E agrees with the observations 

 and drawings of Preyer. The centre of the band between b and F corre- 

 sponds to wave-length 502. According to Preyer its centre corresponds to 

 wave-length 505, i.e. it is somewhat nearer to b. 



1 Hoppe-Seyler, Centralblatt f. d. med. Wissenschaften, 1864. 



2 Hoppe-Seyler, Med. Chem. Untersuchungen, Heft in. (1868) p. 378. 



