64 HISTOLOGY <>/" Xl'TK/KXT I^Ll'/DS. 



V. H/K.MATuBLASTS. 



In addition to the white and red corpuscles of blood, some 

 histologists describe certain pale circular and oval discs in fresh 

 blood, of small size, under the term haematoblasts, or blood 

 plates. According to Ranvier, these seem to be centers of 

 coagulation, as crystals of salt in a solution of the same salt 

 act as centers of crystallization. The name haematoblasts 

 was given by Hayem, who considered them intermediate 

 forms in the development of red corpuscles. 



VI. BLOOD CRYSTALS. 



The chemical constitution of the blood has been an object 

 of much research, especially with the spectroscope. So deli- 

 cate is this mode of analysis that old blood stains on iron, 

 wood, or linen, may be demonstrated by the chemist for the 

 purpose of jurisprudence, by the absorption lines of haemo- 

 globin, consisting of two large dark bands to the right of the 

 sodium line(Frahenhofer's line D) being observed in the spectrum. 

 But the best test of the presence of blood is finding haemin crys- 

 tals under the microscope. This will, however, be no discrim- 

 ination between human and animal blood. A drop of blood is 

 dried upon a slide, a small quantity is then scraped off and 

 placed upon another slide, and a small quantity of sodium 

 chloride added. To this add a few drops of glacial acetic acid, 

 put on a cover glass and warm the slide over a spirit lamp 

 until air bubbles appear. The haemin crystals are in the form of 

 rhombic plates, varying in color from bright yellow to dark 

 brown. Old blood stains on clothing, etc., should be cut out 

 and boiled in glacial acetic acid with a little sodium chloride. 

 After evaporation the crystals are deposited. The haemin 

 which crystallizes in this way is the hydrochlorate of haematin. 

 Haematin is the coloring matter of the blood, which forms 

 spontaneously in effusions of blood within the tissues and in 

 blood kept for a long time in vessels. It is always amorphous and 

 of a deep red color. Haematin, sometimes called haematosine^ 

 united with globulin a substance resembling casein forms 

 haemoglobin, the most important constituent of the blood discs. 

 It used to be called haemato globulin, and haemato crystal- 



