DEVELOPMENT OF THE RED DISKS. 243 



If blood or dry hseraatin be mixed with a small quantity of 

 common salt, a drop of glacial acetic acid 

 added, and the mixture boiled, small char- FIG. 108. 



acteristic crystals appear which have been 

 found to be produced by the union of two 

 molecules of hydrochloric acid with the 

 hsematin. 



The formation of these crystals is very 

 easily accomplished with a small quantity Hsemin Crystals, 

 of old dried blood ; therefore this substance 

 becomes, in medico-legal inquiries, an important test for blood 

 stains. 



Crystals of a substance called Haematoidin are formed in old 

 blood cots retained in the body. It does not contain any iron, 

 and has the chemical formula CaaHgeN^e. It is probably iden- 

 tical with bilirubin, one of the coloring matters found in bile. 



GLOBIN. 



This name has been given by Preyer to the proteid part of 

 the haemoglobin, on account of its slightly differing from glob- 

 ulin, though it resembles it in being precipitated by the weakest 

 acids, even carbon dioxide. 



CHEMISTRY OF THE STROMA. 



The stroma forms only about 10 per cent, of the solid parts of 

 the corpuscles, the rest being haemoglobin. The proteid basis of 

 the stroma is probably mostly made up of a globulin, also con- 

 taining lecithin, cholesterin, and fats in minute proportions. There 

 is little more than one-half per cent, of inorganic salts in the 

 red blood corpuscles, of which more than half consists of potas- 

 sium phosphate and chloride. 



DEVELOPMENT OF THE KED DISKS. 



In the early days of the embryo the blood vessels and corpuscles 

 appear to be formed at the same time from the middle layer of 

 the blastoderm (mesoblast). They first consist of round, nucleated, 

 colorless cells, which subsequently become colored, gradually lose 



