332 THE BLOOD. 



dilute mineral acids, or with stronger solutions of the alkaline 

 hydrates, as also by peptic or tryptic digestion. To obtain the sub- 

 stance in a pure state, however, it is best to start with its hydro- 

 chlorate anhydride, hcemin, which can be readily obtained in crystal- 

 line form. To this end, oxyhsemoglobin is treated with a trace of 

 sodium chloride and dissolved in glacial acetic acid. On heating, 

 the bsemin is precipitated in the form of very characteristic, drawn- 

 out, rhombic platelets, which are insoluble in water, alcohol, and 

 ether, with difficulty so in glacial acetic acid and in dilute mineral 

 acids, but are readily soluble in dilute alkaline solutions and acid 

 alcohol. The crystals are collected on a filter, washed with alcohol 

 and- ether, and are thus obtained in pure form. To prepare the 

 hsematin, the hsemin is dissolved in a dilute solution of sodium 

 hydrate and supersaturated with dilute hydrochloric acid. The sub- 

 stance is thus precipitated in the form of brownish flakes, which are 

 washed free from chlorides and dried at 120 C. Hsematin, in con- 

 tradistinction to oxy hemoglobin and hsemin, is non-crystallizable. 

 Its solubility is essentially the same as that of hsemin. In acid solu- 

 tion both hsematin and hsemin show a well-defined spectral band 

 between C and D. Between D and F a second band is seen, which 

 is much wider but less sharply defined than the first. By diluting 

 "the solution this band may be resolved into three bands, of which 

 one is located between b and F, near F ; another, between D and E, 

 nearer E ; and a third faint band between D and E, nearer D. As 

 a rule, however, only two bands are seen. The alkaline solutions of 

 hsematin are distinctly dichrotic and give only one band of absorp- 

 tion, the greater portion of which lies between C and D, and extends 

 slightly beyond D. 



On careful oxidation hsematin may give rise to an iron-containing 

 body and dibasic haematinic acid, C 8 H 10 O 5 , which can be further 

 transformed into the tribasic acid, C 8 H 10 O 6 . Of the nature of these 

 substances, however, but little is known. Of greater interest is the 

 fact that on treatment with concentrated sulphuric acid, with hydro- 

 chloric acid, or with glacial acetic acid and hydrobromic acid, 

 hsematin as well as hsemin is freed from iron, and on the subsequent 

 addition of water is transformed into hsematoporphyrin, C 32 H 36 N 4 O 6 , 

 which is isomeric with bilirubin (see below). 



Hsematin is thus a decomposition-product of oxyhsemoglobin, and 

 is not found as such in the circulating blood. It is said to occur in 

 the urine, however, in cases of poisoning with arsenious hydride. 

 In the stools it is found after hemorrhages into the stomach or the 

 upper portion of the small intestine, and also after the ingestion of 

 large amounts of red meats. In such cases, of course, its origin is 

 referable to the decomposition of hsemoglobin through the agency of 

 the gastric and pancreatic juices. 



Isolation of Oxyhaemoglobin. Oxyhsemoglobin in crystalline form 

 is best obtained from the red corpuscles of the horse or dog, 

 according to the following method : the blood is first rendered 



