THE BLOOD. 253 



drugs, in cysts and in the urine in hematuria and hemoglobinuria. 

 It is also produced when a solution of hemoglobin is exposed to the 

 air and becomes acid in reaction and brown in color. The spectrum 

 shows two absorption bands similar to oxyhemoglobin, but in addition 

 a new and quite distinct band near the line C, in the red. If the 

 acid solution be rendered alkaline by the addition of ammonia, this 

 band disappears and another makes its appearance near the line D. 

 The addition of ammonium sulphid develops reduced hemoglobin, 

 which, on the absorption of oxygen, produces again oxyhemoglobin, 

 as shown by the spectroscope. 



Hematin. Boiling^ hemoglobin or adding to it acids or alka- 

 lies decomposes IF and Tevelops^ one or more proteid bodies to IL 

 which the general term globulin has been on'vpnfa.nH pm iron -fr old in v 

 pigment termed heoaatinjt This is regarded as an oxidation product 

 oi h'emoglobin and constitutes about 4 per cent, of its composition. 

 When obtained in a pure state, it is a non-crystallizable blue-black 

 powder with a metallic luster. According^as~it is treated with acids or 

 alkalies, two forms of hematin can be obtained (acid and alkaline), 

 each of which has special properties, giving rise to different absorp- 

 tion bands. 



Hemochromogen. This pigment is derived from hemoglobin, 

 of which it constitutes about 96 per cent., during decomposition in 

 the absence of oxygen. In solution it produces a purple color, but 

 soon absorbs oxygen and is converted into hematin. 



Hemin. This pigment is a derivative of hematin, presenting 

 itself in the form of microscopic rhombic plates or rods (Teichmann's ^ 

 ^crv^tals], which are so characteristic as to serve as testsTbr"blcxk!F 

 stains in medico-legal inquiries. These crystals are readily obtained 

 by adding to a small quantity of_dried blood oiLja glass slide"a few 

 drops of glacial acetic acid and a crystal of sodium chlorid; after 

 heating gently for a few minutes over a spirit lamp and then allowing 

 the mixture to cool, crystallization of the hemin soon takes place. 



Hematoidin. This term has been applied to a pigment which 

 occurs in the form of yellow crystals in old blood- clots or in blood 

 which has been extravasated into the tissues. In its chemic com- 

 position and in its reactions it closely resembles bilirubin, the pigment 

 of the bile, exhibiting the same characteristic play of colors on the 

 addition of nitric acid. 



The Stroma. The stroma of the red corpuscles obtained by the 

 methods which dissolve out the hemoglobin has been shown by 

 analysis to consist of from 60 to 70 per cent, of water and 40 to 30 

 per cent, of solid material, containing a proteid resembling cell- 

 globulin, lecithin, cholesterin, and inorganic salts, among which 

 potassium phosphate is especially abundant. 



