94 HAND-BOOK OF PHYSIOLOGY. 



ing ammonium sulphide, reduced haemoglobin is produced, and on shaking 

 this up with air, oxyhsemoglobin. is reproduced. 



Haematin. By the action of heat, or of acids or alkalies in the pres- 

 ence of oxygen, haemoglobin can be split up into a substance called 

 H&matin, which contains all the iron of the haemoglobin from which it 

 was derived, and a proteid residue. Of the latter it is impossible to say 

 more than that it is probably made up of one or more bodies of the globu- 

 lin class. If there be no oxygen present, instead of haematin a body called 

 hcemocliromogen is produced, which, however, will speedily undergo oxi- 

 dation into haematin. 



Haematin is a dark brownish or black non-crystallizable substance of 

 metallic lustre. Its percentage composition is C. 64-30; H. 5 -50; N. 9 -06; 

 Fe, 8-82; 0. 12-32; which gives the formula C 68 , H 70 , N 8 , Fe 2 , 10 (Hoppe- 

 Seyler). It is insoluble in water, alcohol, and ether; soluble in the 

 caustic alkalies; soluble with difficulty in hot alcohol to which is added 

 sulphuric acid. The iron may be removed from haematin by heating it 

 with fuming hydrochloric acid to 320 F. (160 C.), and a new body, 

 hcematoporpliyrin, is produced. 



In acid solution. If to blood an excess of acetic acid be added, the 

 color alters to brown from decomposition of haemoglobin, and' the setting 

 free of haematin; by shaking this solution with ether, solution of the 

 haematin is obtained. The spectrum of the etherial solution shows no 

 less than four absorption bands, viz., one in the red between c and D, one 

 faint and narrow close to D, and then two broader bands, one between D 

 and E, and another nearly midway between I and F. The first band is 

 by far the most distinct, and the acid solution of haematin without ether 

 shows it plainly. 



In alkaline solution. The absorption band is still in the red, but 

 nearer to D, and the blue end of the spectrum is partially absorbed to a 

 considerable extent. If a reducing agent be added, two bands resembling 

 those of oxyhaemoglobin, but nearer to the blue, appear; this is the spec- 

 trum of reduced hcematin. On shaking the reduced haematin with air or 

 oxygen the two bands are replaced by the single band of alkaline 

 haematin. 



Hsematoidin. This substance is found in the form of yellowish 

 crystals in old blood extravasations, and is derived from the haemoglobin. 

 Their crystalline form and the reaction they give with nitric acid seem to 

 show them to be identical with Bilirubin, the chief coloring matter of 

 the Bile. 



Hsemin. One of the most important derivatives of nsematin is 

 Haemin. It is usually called Hydrochlorate of Hcematin (or hydrochlo- 

 ride), but its exact chemical composition is uncertain. Its formula is C 0fJ , 

 H 70 , N 8 , Fe 2 , 10 , 2 Hcl, and it contains 5*18 per cent, of chlorine, but 

 by some it is looked upon as simply crystallized hamiatin. Although 



