Principles Of Veterinary sUrGErV 45 



Chemotaxis is the principal cause of the emigration. This is 

 the phenomenon shown by Hving cells (phagocytes) of mov- 

 ing toward (positive) or away from (negative) certain other 

 cells or substances. The positive chemotaxis exerted by the 

 inflammatory irritant attracts the leucocyte, which is ever 

 looking for food-stufif and debris. The exact explanation of 

 chemotaxis is not definitely given. MetchnikofT suggests 

 that this phenomenon is similar to the action of the plant 

 reaching upward, the root penetrating downward or the leaf 

 turning toward the light. It is known that certain leuco- 

 cytes are attracted toward bacteria which they pick up into 

 their protoplasm, and attempt to destroy by a ferment which 

 they possess, called "cytase." This is phagocytosis. There 

 are two kinds of phagocytes- — the polymorphonuclear leuco- 

 cytes, or "microphages," with a ferment called microcytase, 

 and the lymphocytes, endothelial cells, and fibroblasts, or 

 "macrophages" whose ferment is called "macrocytase." 

 This cytase is the alexin of Buchner, or complement of Ehr- 

 lich. It has been given several names by other authors. 

 Cytase enters largely into the action of anti-bodies, which 

 play such an important part in immunity. 



The kind of leucocyte which emigrates in inflammation 

 depends upon the irritant. The most common cell is the 

 poljonorphonuclear leucocyte. In acute inflammations, es- 

 pecially pyogenic, these cells are attracted into the tissue in 

 large numbers ; and, together with degenerative changes in 

 the tissue, viz., liquefaction necrosis, form pus. In catarrhal 

 inflammation, mucous membrane is the seat of the reaction. 

 Here the leucocytes collect in fairly large numbers and the 

 degeneration of the epithelial cells is slight. In every inflam- 

 mation, more or less of these leucocytes are present. They 

 will be found especially in the neighborhood of the blood- 

 vessels. They have the same characteristic appearance, even 

 when degenerated, as in the blood. A few eosinophilic leu- 



