402 



a series of neAv compounds, produced by the more complete 

 oxidization of the colouring matter of blood ; but these differ 

 from that just described in not being restored to the original 

 state by deoxidization, as though the Avhole molecular con- 

 stitution of the haemoglobin were changed. So far I have 

 succeeded in preparing at least four such substances. Three 

 of these resemble one another in having oxidized and de- 

 oxidized modifications, and when in the latter state in an 

 alkaline solution in being of a dull olive-green colour, with a 

 single absorption-band in their spectra; but they are dis- 

 tinguished from one another by these bands being situated in 

 the red, in the orange, and in the yellow, respectively, as 

 well as by other peculiarities. 



There are other products which do not give rise to spectra 

 with definite absorption-bands, but merely cut off more or 

 less of the blue end, and are thus analogous to those sub- 

 stances so often formed by that amount of the oxidization of 

 colouring matters which just precedes complete loss of colour. 

 Such a compound occurs in moderately old blood-stains, and 

 is the chief constituent of some which have been kept many 

 years. My object now is to examine how far these various 

 products of more or less complete oxidization may correspond 

 Avith any colours formed naturally in normal or abnormal con- 

 ditions of the blood or secretions ; but before doing this I 

 thought it desirable to further investigate such artificially 

 prepared substances, since I have good reason for believing 

 that several others exist, not yet completely understood, which 

 give rise to spectra with special characteristic absorption- 

 bands. 



Note on Methjemoglgbin, By E. Ray Lankester. 



Hoppe-Seyler describes Methsemoglobin as an interme- 

 diate product of the spontaneous change of Haemoglobin into 

 Hsematin. He states that it is soluble in water, is charac- 

 terised by an absorption-band in red, like that of acid 

 Haematin, and is precipitated by acetate of lead. He appears 

 to have seen it only in mixture Avith Hemoglobin, and doubts 

 its distinct existence. Preyer, Avriting since in Pfluger's 

 * Archiv,' describes Methsemoglobin as produced from Heemo- 

 globin either by ozone, carbonic acid gas, or spontaneous 

 change in a dry chamber. He says it is 7iot precipitated by 



