HAEMOGLOBIN (REDUCED HAEMOGLOBIN). 231 



(g) Solution of sodium hydrosulpliite (NaHS0 3 ). By the action of metallic 

 zinc on a solution of sodium sulphate, in the absence of oxygen, a solution of 

 intense reducing power is retained. Such a solution, which instantly decolor- 

 ises indigo and litmus, reduces oxy haemoglobin. 1 



Methods of determining the percentage of haemoglobin have been based on 

 this reaction, 2 3 though they have been abandoned as unreliable. 4 



(li) Solution of hydrazin and its salts. It was pointed out by Curtius 5 that 

 a solution of a salt of hydrazin reduces solutions of oxy haemoglobin with great 

 rapidity ; and Hiifner 6 afterwards employed an aqueous solution of hydrazin 

 hydrate to effect the reduction of concentrated solutions of oxyhaemoglobin, 

 the advantages of this reducing agent being that the only products of its 

 decomposition are nitrogen and water, as shown in the following equation : 



H 2 N NH 2 .H 2 + 2 = Na + 3H 2 0. 



(hydrazin hydrate) 



2. By taking advantage of the reducing action exerted by pro- 

 ducts of putrefaction. The solutions of oxyhaemoglobin, or of diluted 

 blood, is set aside in sealed tubes, when, especially at temperatures ap- 

 proaching 40 C., reduction rapidly occurs. It is worthy of remark that, 

 whilst oxyhsemoglobin or its solutions very rapidly undergo change at 

 temperatures above C., such is not the case with reduced haemoglobin, 

 which may be kept for many years in sealed tubes in the presence of 

 putrefactive bacteria and the products of their activity. On opening the 

 tubes and agitating with air, oxyhsemoglobin is at once formed, and under 

 favourable conditions may be crystallised. 



3. By taking advantage of the conditions which favour the 

 "dissociation" of the compound of O 2 with haemoglobin. (a) By 

 boiling in a "Toricellian" or barometric vacuum; (&) by subjecting 

 diluted blood or a solution of oxyhaemoglobin to the action of a 

 long-continued stream of a neutral gas, such as hydrogen, nitrogen, or 

 nitrous acid. 



4. By temporarily arresting the circulation through a suffi- 

 ciently transparent part of the animal body. It was first pointed 

 out by Vierordt, 7 that the spectrum of oxyhaemoglobin can be satisfac- 

 torily demonstrated by bringing two fingers (preferably the fourth and 

 fifth) close together and passing a beam of sunlight through the com- 

 paratively thin layer of tissues at the boundaries of the adjacent fingers. 

 He further pointed out that, on placing caoutchouc rings at the base of 

 the first phalanges, after an interval varying between 40 and 300 

 seconds (?), the two bands of oxyhaemoglobin became replaced by the 

 single band indicative of reduced haemoglobin. 8 



1 Schiitzenberger and Risler, " Recherches sur le pouvoir oxydant du sang," Compt. rend. 

 Acad. d. sc., Paris, 1873, tome Ixxvi. pp. 440-442, and pp. 1214-1216. 



2 Rollett, loc. cit. 



3 Ludwig and Schmidt, loc. cit. 



4 Qninquaud, "Sur un precede de dosage de I'he'moglobine dans le sang," Compt. rend. 

 Acad. d. sc., Paris, 1877, tome Ixxvi. p. 1489. 



5 Journ. f. prakt. Chem., Leipzig, 1889, Bd. xxxix. S. 27. 



6 " Bestimmung d. Sauerstoffscapacitat d. Blutfarbstoffs, " S. 156. 



7 "Das Hamoglobinspectrum am lebenden Menschen," Ztschr. f. Biol., Mitnchen, 1876, 

 Bd. xi. S. 188 ; and "Die Sauerstoffzehrung der lebenden Gewebe," ibid., 1878, Bd. xiv. 

 S. 422. 



8 Refer to the following papers by A. Henocque, " fitude spectroscopique du sang a la 

 surface sous-ungueale du pouce," Compt. fend. Soc. de biol., Paris, Ser. 8, tome i. p. 671 ; 

 and also "Notes complernentaires," ibid., p. 700. According to this author, the average 

 time of reduction, when the circulation through the thumb is arrested, varies between fifty- 

 five and sixty- five seconds. 



