120 HAEMATOIDIN. [BOOK I. 



first becomes reduced, and thereafter the oxygen contained in the air 

 of the tube is removed by it. When many days have elapsed and 

 the whole of the haemoglobin is reduced, the tubes are reversed and their 

 contents mixed, when the optical properties of haemochromogen can 

 be satisfactorily observed. 



According to Jaderholm 1 , Hoppe-Seyler's haemochromogen in alkaline 

 solution is identical with the reduced haematin of Stokes, and haemochro- 

 mogen in acid solution has a spectrum which is a combination of those of 

 acid haematin and haematoporphyrin. The former statement is indeed 

 admitted by Hoppe-Seyler, and is indisputable. Hoppe-Seyler urges, how- 

 ever, and as it appears to the Author, most correctly, that the term reduced 

 haematin is a misleading one, haemochromogen being a mere product of 

 decomposition of haemoglobin, whilst haematin is an oxidized product of 

 decomposition. 



Haematoidin. 



This name has been assigned by Virchow 2 to a substance which 

 occurs in the form of yellow microscopic crystals in old extravasations 

 of blood, as for example in old apoplectic clots, and which was first 

 observed by Everard Home 3 . 



FIG. 26. CRYSTALS OF HAEMATOIDIN (AFTER FUNKE). (Frey.) 



These crystals appear to be identical in form with those of Biliru- 

 bin, the chief colouring matter of human bile, and when treated with 

 fuming nitric acid give the same colour reaction (Gmelin's reaction). 



Opinions have been divided on the question of the 



identity identity or non-identity of haematoidin and bilirubin. 



din and wii- On ^ ne g roun d of different deportment towards solvents 



rubin. Holm 4 asserted that haematoidin, prepared from the 



1 Jaderholm, " Untersuclmngen iiber den Blutfarbstoff und dessen Zersetzungspro- 

 ducte." Abstracted from the Swedish by Hammarsten in Maly's Jahresbericht, Vol. 

 vi. p. 85. 



a Virchow, Archiv d. pathol. Anat. u. PhysioL Vol. 1 (1847), p. 383443. 



3 Sir Everard Home, A short tract on the Formation of Tumours, &c. London, 1830, 

 page 22. In Figs. 1, 2 and 3 of Plate I., crystals of haematoidin are admirably figured 

 as seen in an aneurismal coagulum. Home was, however, altogether ignorant of their 

 nature and referred to them as ' crystallized salts. ' 



* Holm, "Haematoidin," Journ. f.prak. Chemie. Vol. c. p. 142. 



