220 OXY-H.EMOGLOBIN. 



The spectroscopic appearances of solutions of oxy-haemoglobin 

 have been already sufficiently described and figured ( 345). (For 

 convenience of reference Fig. 75 is reproduced here.) When its 

 solutions are heated or it is treated either in solution or as a solid 

 with_ acids or alkalis, it may be readily decomposed, yielding a 

 proteid as in the case of haemoglobin and a coloured residue, viz. 

 naematin. (See below.) The oxygen which is loosely combined 

 with haemoglobin in the formation of oxy-haemoglobin may be 

 readily removed by several means of which the following are 

 those most usually employed. 



(i) The solution is warmed to 40 and the gas driven off by 

 exposure to the vacuum of a mercurial pump, (ii) A current of 

 some neutral gas such as hydrogen or nitrogen is passed through 

 the solution, (iii) The solution is treated with a few drops of 

 some reducing agent such as Stokes' fluid. 1 This is prepared by 

 adding tartaric or citric acid to a solution of ferrous sulphate, and 

 then ammonia until it is strongly alkaline. This reagent does not 

 keep and must be freshly prepared each time it is required. In- 

 stead of Stokes' fluid, ammonium sulphide may be used, but in 

 this case some slight manipulation is frequently required to ensure 

 reduction. A few drops of the sulphide are added to the solution, 

 which is then gently warmed : if on examination with the spectro- 

 scope it is found that the reduction has not taken place, as shown 

 by the persistence of the two bands of oxy-haemoglobin, a little 

 more of the sulphide may be added and the mixture again care- 

 fully warmed. 



The amount of oxygen, removable by the means just described, 

 with which one gram of haemoglobin (from dog's blood) can unite 

 is usually stated as being T59 c.c. at and 760 mm. Hg. this 

 constant being taken as independent of the concentration of the 

 solutions employed. 2 Quite recently some doubt has been cast on 

 the quantity being thus constant ; and it has been stated that 

 several modifications of haemoglobin exist which, while they can- 

 not be discriminated by their purely chemical characteristics, 

 exhibit a marked difference as to the amount of oxygen with 

 which the same quantity of each can unite under similar external 

 conditions ; the results thus obtained are stated to hold good for 

 the compound of oxygen with haemoglobin as it exists in the red 

 blood-corpuscles of the dog, 3 and further for the haemoglobin of 

 guinea-pigs and geese. 4 Further investigation must decide the 

 interesting questions raised by the above statements. 



There appears to be a consensus of opinion that haemoglobin, 

 and more particularly oxy-haemoglobint possesses to a slight 



1 Proc. Roy. Soc. June, 1864. Phil. May. November, 1864. 



2 Hiifner, Zt. f. physiol. Chem. Bd. i.' (1878), Sn. 317, 386. See also Jn. f. 

 prakt. Chem. Bd. xxn. (1880), S. 362. 



3 Bohr u. Tornp, Skandinav. Arch. f. PJnjsiol. Bd. HI. Hft. 1, 2 (1891), S. 69. 

 Bohr, Ibid. Sn. 76, 101. 



4 Jolin, Arch.f. Physiol. Jahrg. 1889, S. 265. 



