464 THE BLOOD [CFl. XXIX. 



haematin and globin; a hydroxyl group of the hsematin is then 

 replaced by chlorine; it is similarly easily replaceable by an atom 

 of bromine or iodine. Nencki and Zaleski have further shown that 

 when prepared in this way, hsemin also contains an acetyl group. 

 It has the empirical formula C 34 H 32or34 4 N 4 FeCl. 



Hsematoporphyrin, C 34 H 3 80 6 N 4 , is iron-free haematin ; it may be 

 prepared by mixing blood with strong sulphuric acid ; the iron is 

 taken out as ferrous sulphate. It is also found sometimes in nature ; 



FIG. 330. Hsemin crystals. (Frey.) FIG. 331. Hsematoidin crystals. 



(Frey.) 



it occurs in certain invertebrate pigments, and may also be found in 

 certain forms of pathological urine. Even normal urine contains 

 traces of it. It presents different spectroscopic appearances accord- 

 ing as it is dissolved in acid or alkaline media. The absorption 

 spectrum figured (No. 9) is that of acid haematoporphyrin. 



If oxyhaemoglobin is treated with dilute acids the result is a formation of 

 haematin and globin, but if strong sulphuric acid is employed the iron is removed 

 from the haematin and so haematoporphyrin is obtained. The stability of the iron 

 in the molecule is due to the presence of oxygen, for with the reduced pigment, 

 haematoporphyrin is obtained even when dilute acids are employed. Pure haemato- 

 porphyrin can once more be converted into haematin (that is, the iron can be replaced) 

 by warming a solution in dilute ammonia and adding a little Stokes' fluid, and a few 

 drops of a reducing agent such as hydrazine hydrate. If cuprammonium solution is 

 used instead of Stokes' fluid in this experiment, a copper compound of haemato- 

 porphyrin is obtained, which is identical with turacin, the bright red copper-containing 

 pigment found in the plumage of the plantain-eating birds. (Laidlaw.) 



Hcemopyrrol is a substance obtained by reduction from haematoporphyrin. It 

 is dimethyl-ethyl pyrrol, and its formula is : 



CH 3 .C 

 CH 3 .C 



C.C 2 H 5 



CH 



1STH 



There is a near relationship between haemoglobin and chlorophyll, for 

 the same substance is obtained from phylloporphyrin, C 16 H 18 N.X), a derivative of 

 chlorophyll. Chlorophyll, however, contains no iron. 



Haematoidin. This substance is found in the form of yellowish 

 red crystals (fig. 331) in old blood extravasations, and is derived from 

 the haemoglobin. Its crystalline form and the reaction it gives with 



