160 PRINCIPLES OF VETERINARY SURGERY 



munity, and the entire scientific world admits it to be at 

 least a link in the solution of a most complex and interesting 

 problem, one which deals with the vital welfare of all the 

 domestic animals and man. 



If a few anthrax bacilli are introduced into the body of 

 an animal, it will be soon noticed that some of the leuco- 

 cytes are attracted by the chemotactic influence of the bac- 

 teria. The cells pick up the bacteria, incorporate them 

 into their protoplasm and digest them by means of a fer- 

 ment which they possess called cytase. All cells which pick 

 up and digest bacteria are called phagocytes. Metchnikofif 

 describes two kinds, the microphages and macrophages. 

 The microphage is the polymorphonuclear leucocyte, with 

 its irregular lobulated nucleus, which is regarded as an 

 adaptation to enable the cell to pass as rapidly as possible 

 through the walls of the capillaries and venules. This active 

 process is called amoeboid movement. The macrophages 

 consist of the mononuclear leucocytes or the so-called large 

 lymphocytes. Other cells have phagocytic properties also, 

 such as fibroblasts and endothelial cells, but they have little 

 or no power of movement. 



Phagocytosis Metchnikofif states to be one of the 

 principal means of defence possessed by an animal. As 

 soon as bacteria have penetrated the body, a whole army 

 of leucocytes proceeds toward the point of invasion, and 

 there enters upon a struggle with the micro-organisms. 

 The macrophages follow the microphages and become 

 mixed in greater or less numbers with the exudation. The 

 leucocytes having arrived at the spot where the bacteria 

 are found, seize them within their bodies and subject them 

 to intercellular digestion. This digestion takes place in the 

 vacuoles, which usually contain a weakly acid fluid con- 

 taining ferments. Micro-organisms attract not only leu- 

 cocytes, but .also other bodies, inert particles of dust 



