1302 



H^MATOIDIN. 



and lies midway between D and E. By the addition of water 

 to the solution in sulphuric acid the colouring matter is largely 

 precipitated, especially if some alkali be carefully added to 

 neutralize the acid. The precipitate thus obtained is readily 

 soluble in dilute alkalis, and this solution is characterized by 

 four absorption bands, one half-way between C and D, two 

 between D and E, and one conspicuous band adjoining b and 

 extending nearly to F. Acid and alkaline solutions of haemato- 

 porphyrin show an absorption band in the extreme violet 

 between h and H. Haematin also yields haematoporphyrin by 

 the action of strong hydrochloric acid at 130 in sealed tubes. 



Some interest attaches to this substance owing to its not 

 infrequent occurrence in minute quantity in normal urine and 

 in larger amounts in the urine of many diseases in forms which 

 may shew slightly different absorption spectra but are probably 

 closely related if not identical. It is stated to be markedly 

 present in urine after the administration of sulphonal and has 

 then been obtained in a crystalline form. It is also found in 

 the integument of some invertebrates and in the egg-shells of 

 certain birds. It is further interesting to notice that in haema- 

 toporphyrin we have a strongly coloured pigment derived from 

 haematin with removal of the iron which the latter contains, a 

 fact which facilitates our conception of a possible derivation of 

 the iron-free bile-pigments from the iron-containing haemoglobin 

 or haematin. 





13. Haematoidin. 



C 16 H 18 N 2 3 . 



This substance is found as reddish or orange rhombohedral 

 crystals in old blood-clots as of cerebral haemorrhages, in cor- 

 pora lutea, in the urine in cases of transfusion of blood and in 



FIG. 233. H^EMATOIDIN CRYSTALS. (Frey after Funke. ) 



cases of hsematuria. There is no doubt that as occurring in the 

 above cases it is directly derived from some metamorphosis of 

 haemoglobin. Apart from the similarity of crystalline form 



