HMMOCHROMQGMN. 257 



When subjected to the action of such reducing agents as tin and 

 hydrochloric acid, hsemochromogen gives rise to coloured products, which 

 are obviously nearly related to, though not identical with, such bodies as 

 the so-called urobilins. 



It was stated that when blood saturated with CO, or a concentrated 

 solution of CO-haemoglobm, is treated with a concentrated solution of 

 sodium hydrate, a bright red precipitate separates. Jaderholm stated 

 that this precipitate consisted of a compound of CO with hsematin, and 

 could be prepared directly by the action of the gas on a solution of 

 reduced haematin ; he further asserted that the visible absorption- 

 spectrum of the CO-haematin closely resembled that of CO-haemoglobin, 

 the bands occupying the same position ; though he described them as 

 being less intense in the haematin compound, and as differing from the 

 CO-haemoglobm compound in the fact that the two bands and 13 

 exhibit equal intensities. 



By causing an alkaline hydrate to act upon CO -haemoglobin in the 

 absence of oxygen (method with double tubes previously described), and 

 heating to 100 C., Hoppe-Seyler separated the body which Jader- 

 holm had described as CO-haematin, but which appears really to be 

 CO-haemochromogen. Like haemoehromogen itself, its CO -compound, 

 which has been deposited at 100 C., dissolves again when 

 the liquid from which it separates cools. The CO-compound of 

 haemochromogen is described by Hoppe-Seyler as a crystalline body, 

 though none of its physical characters have been subjected to even a 

 superficial examination. The visible spectrum of its solution is, accord- 

 ing to Hoppe-Seyler, absolutely undistinguishable from that of CO- 

 hsemoglobin. 



The most interesting and weighty observation made by Hoppe- 

 Seyler on this subject was, however, that concerning the volume of CO 

 which combines with haemochromogen to form its CO -combination. He 

 found that the same volume of CO combines with haemochromogen. as 

 would be required to convert an equivalent weight of reduced haemo- 

 globin into the CO-compound. This unquestionably interesting ob- 

 servation, taken in connection with the fact that crystals form under 

 certain circumstances in solutions which contain CO-haemochromogen 

 (there is no absolute proof that the crystals represent this substance), 

 led Hoppe-Seyler to form certain hypotheses of extraordinary boldness, 

 for which the experimental bases are as yet altogether wanting, but 

 which have been accepted with misplaced confidence ; these hypotheses 

 he looked upon as legitimate conclusions from his own experiments, and 

 formulated as follows : 



" We are justified in concluding that in crystallised CO-hsemoglobin, 

 as well as in the colouring matter of the blood corpuscles, there is 

 present a particular group of atoms which combines with and retains 

 carbonic oxide, which is characterised by the special manner in which it 

 absorbs light, and which, after separation from the albuminous residues, 

 passes unchanged into CO-haemochromogen. 



" Without possibility of doubt, this group of atoms is identical with 

 the one which, in the arterial blood-colouring matter, 1 and in crystallised 

 oxyhaemoglobin, holds two atoms of oxygen in combination, in the place 

 of a molecule of CO. 



" The oxyhaemoglobins, the haemoglobins, and the CO-hsemoglobins, as 



1 Reference is here made to the hypothetical "arterin." 

 VOL. I. 17 



