84 THE BLOOD. 



decomposition, and not the pure and unaltered colouring 

 matter, for which he proposes the name of cruorin. 



As, however, heematin must of necessity be very closely 

 allied to cruorin, even if it be not identical with it, it 

 may be well to enumerate its principal characters. In the 

 purest state in which it can be obtained, it is so far 

 changed as to be insoluble in water, of a deep blackish 

 brown colour, and not liable to change of colour on 

 exposure to gases. Boiling alcohol will dissolve small 

 quantities of it, and it is freely soluble in alcohol acidulated 

 with sulphuric, hydrochloric, or nitric acid, and in weak 

 solutions of potash, soda, or ammonia. According to 

 Mulder, pure hsematin consists of carbon, 65-84 percent.; 

 hydrogen, 5^37; nitrogen, 10-4; oxygen, ii'75 ; iron, 

 6-64. The presence of so large a proportion of iron con- 

 stitutes a peculiar feature in heematin. The mode in 

 which the metal exists in it has been much discussed. By 

 some it is supposed to be in the form of an oxide, or a salt, 

 or in the form of peroxide in arterial blood, and carbonate 

 of the protoxide of iron in venous blood (Liebig). But 

 the greater probability is that the iron is combined as an 

 element with the four essential elements, carbon, hydro- 

 gen, nitrogen, and oxygen, in the same manner as, it is 

 believed, sulphur is combined with them in albumen, 

 fibrin, cystic oxide, etc., or as iron in ferrocyanogen. The 

 principal evidence for this view, which is especially sup- 

 ported by Scherer and Mulder, is, i, that when chlorine, 

 which would not decompose an oxide of iron, is passed 

 through a solution of haematin, chloride of iron is formed, 

 and the iron, thus removed from the other elements of the 

 haematin, is replaced by chlorous acid ; 2, that all the iron 

 may be removed from heematin by sulphuric acid, without 

 abstracting from it any of its oxygen, which would not be 

 possible if the iron were more intimately united with the 

 oxygen than with the other elements of the hsematin ; 

 3, that pure hsematin may be exposed for several days to 



