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tains excess of ammonia, but soon acts wlien it is neutral, 

 and still more quickly when it contains an excess of such a 

 very weak acid as the boric. A somewhat stronger acid, like 

 benzoic, so far increases the oxidizing power that the haemo- 

 globin is quite decomposed. I have succeeded in obtaining 

 this compound by means of a great variety of oxidizing re- 

 agents. It may be obtained very free from other coloured 

 products by keeping for some days a solution of fresh blood 

 Avith manganese — manganic oxide, prepared by calcining the 

 carbonate in an open crucible. The colour of the solution 

 is gradually changed from red to a sort of orange-brown, 

 and it then shows to great advantage a spectrum with four 

 absorption-bands, the most distinct of which is situated in 

 the red. This spectrum is not nearly so Avell seen when 

 nitrite of potash is added to a solution of blood, since it is 

 then in rather too alkaline a condition ; but if a little boric 

 acid be added, the spectra correspond in all essential par- 

 ticulars. 



On keeping this colour produced by the action of nian- 

 ganoso-manganic oxide for a few days in an open tube with 

 iron filings, it is gradually deoxidized, and the colour and 

 spectrum again become exactly the same as those of fresh 

 blood. This and other facts lead me to conclude that it is 

 a sort of joeroxidized haemoglobin, containing more oxygen 

 than is taken up by the deoxidized modification discovered 

 by Stokes, when oxidized by exposure to air ; but still this 

 extra amount of oxygen combines with the haemoglobin 

 withoiTt its molecular constitution being destroyed, for 

 it may be easily reduced to the protoxidized or deoxidized 

 states by weaker or stronger deoxidizing processes. The 

 alkaline solution gives a very characteristic spectrum, dis- 

 tinguished from the simple oxidized haemoglobin by a narroAv 

 absorption-band in the orange. 



Ozone is one of those oxidizing reagents which give rise to 

 the peroxidized haemoglobin, but at the same time to haematin, 

 probably by changing the albuminous constituent of the 

 haemoglobin, and also to products of the more complete 

 oxidization of haematin. This is similar to what occurs when 

 dry blood-stains are exposed to atmospheric air, even in cases 

 where ozone could scarcely be present. The results are very 

 diff'erent when the stains are kept damp. The same sub- 

 stances are also met with in scabs formed over wounds of the 

 flesh, and it remains to be ascertained whether the per- 

 oxidized compound may not be formed in some diseased 

 conditions of the blood. 



In following out these inquiries I have been led to discover 



