120 HISTOLOGY. 



preparations in the blood-vessels, in the red blood-cells of the 

 bony fishes, and sometimes in the liver cells. 



Hcemoglobin is easily broken up into hcematin, hcematoidin, 

 and hcemin. The first is amorphous, but the other two may be 

 crystallized. Hsematoidin appears in the form of rhombic 

 prisms of an orange-red color. These are found in all extrav- 

 asations of blood (e. g., in the corpus hasmorrhagicum of the 

 ovary, and in clots on the brain). Hsemin occurs in the form 

 of rhombic plates lying singly or crossed to form stars. These 

 are called Teichmanrfs crystals. They are colored mahogany- 

 brown, and can be obtained even in blood which has been dried 

 for a long time. They are thus of forensic significance. 

 Their demonstration shows the undoubted presence of blood, 

 but it does not determine that the blood is necessarily human. 

 In making this haBmin test for blood, a small crystal of common 

 salt and two drops of glacial acetic acid are placed on a slide 

 with the suspected material. This mixture is heated to boil- 

 ing-point until the acid is almost evaporated, and is then 

 examined with high magnification. 



2. Lymph. 



The lymph is a colorless fluid whose only cellular elements 

 are the colorless cells called lymphocytes. There are also found 

 in it particles of fat which after fat digestion give to it a white, 

 milky appearance. The fluid part of lymph is called lymph 

 plasma. 



