CHEMICAL BASIS OF THE ANIMAL BODY. 229 



solution of oxy-hsemoglobin add a few drops of a dilute (-5 I'O p.c.) 

 solution of either of the salts and warm very gently. If on examination 

 with a spectroscope the two bands of oxy-hsemoglobin are still strongly 

 visible, let the mixture stand for a short time, and if the band charac- 

 teristic of methsemoglobin has not made its appearance add one or two 

 drops more of the solution of the salt and proceed as before. As soon 

 as the bands of oxy-hsemoglobin have markedly disappeared, acidulate 

 very faintly and examine again. The band which should now be 

 visible as characteristic of met haemoglobin lies in the red part of the 

 spectrum, between C and D, nearer to the former line. As already 

 remarked its position is closely similar to that of hsematin in acid 

 solution, but comparison will show that it lies nearer D than does the 

 haematin band, the centre of the latter being situated at w. L. 640, while 

 that of the former is at w. L. 630 l (see Fig. 37, Nos. 4 and 5). 



In addition to the reagents recommended above an extensive series of other 

 substances are also found to effect the conversion of oxy-haemoglobin into methae- 

 moglobin, such as potassium chlorate, amyl-nitrite, iodine dissolved in potassium 

 iodide, bromine, osmic acid, hydrochinou, pyrocatechin, &c. 2 It may also be 

 obtained as the result of prolonged evacuation with a mercurial pump, of putre- 

 factive changes, or of the action of palladium saturated with hydrogen and 

 immersed in the solution of oxy-hasmoglobin 3 . 



The absorption band which has so far been described is the one 

 which is to be regarded as characteristic of methaemoglobin, being 

 accompanied by a very marked absorption of the violet end of the 

 spectrum extending up to the D line. In addition to this band it 

 is stated that, working with a good spectroscope of low dispersive 

 power, three other bands may be additionally seen 4 , two corresponding 

 closely with those of oxy-hsemoglobin but not identical, their centres 

 corresponding to w. L. 580 and 539, and the third in the blue at w. L. 

 500 (l) 



In an alkaline solution the position of two of these bands differs 

 slightly from that just given, being stated by Jaderholm to be at w. L. 

 602 and 578 while the third is unaltered at 539. 



In the preparation of large quantities of crystallised oxy-hsemoglobin 

 from pig's blood it was observed that during the recrystallising essential 



1 This method of localising the bands means that their centres occupy positions 

 in the spectrum where the wave-length of light is respectively 640 and 625 

 millionths of a millimeter. It should always be adopted for all absorption bands 

 since it is independent of the varying dispersion and arbitrary scales of different 

 spectroscopes. For details see Gamgee, Physlol. Cliem. Vol. i. p. 94. 



2 For list of substances see Hayem, Compt. Rend. T. en. (1886), p. 698. 



3 Hoppe-Seyler, Zt. f. physiol. Chem. Bd. n. (1878), S. 149. 



4 Jaderholm, Zt. f. Biol. Bd. xx. (1884), S. 419. Also Nord. Med. Arkiv. 

 Abst. in Maly's Jahresb. 1884, S. 113. But see also Araki, Zt. f. physiol. Chem. 

 Bd. xiv. (1890), S. 405. 



5 For figure see Halliburton, Chem. Physiol. and Pathol. Fig. 59, Spect. 6, p. 277. 



