INFLAMMATION. 159 



fibrinous exudate of diphtheritic inflammation is verv injurious 

 because of its coagulation and pressure upon the tissues. 



Che.motaxis. — It has been determineil bv exiieriment that 

 chemic substances exert a definite influence upon motile cells. 

 There is always a leucocytic migration into capillary glass tubes 

 previously charged with turpentine or croton oil and then insert- 

 ed into living animal tissues. The same migration is observed 

 when the capillary tubes are charged with bacteria or tlieir 

 products. Negative results are obtained when the tubes are 

 charged with qumine or chloroform. This attraction of leuco- 

 cytes toward chemic substances is positive chemotaxis. The 

 repulsion of leucocytes from chemic substances is negative chem- 

 otaxis. The term "Chemotaxis" unmodified includes positive 

 and negative. Leucocytic migration into an inflammatory area 

 is a result of chemic influence or chemotaxis. 



Phagocytosis. — This is the incorporation and destruction of 

 pathogenic bacteria and other foreign substances by phagocytes. 

 Phagocytes are cells having the power of ingesting and destrov 

 ing microorganisms and other foreign ])articles. Polymorpho- 

 nuclear leucoc}'tes ha\-ing neutropliile granules are the most ac- 

 tive cells concerned in phagocytosis. Enddthelial cells and wan- 

 dering connective tissue cells may be under some conditions 

 phagocytic. The phagocytic property of cells is variable depending 

 upon the virulency of the micro-organisms or strength of the 

 chemic substance and upon the resistance of the phagncvte. Bac- 

 teria are enveloped bv protoplasmic extensions from the cell 

 body until they are entirely included in the aggressive phago- 

 cyte. After the enveloping process there mav be observed diges- 

 tion vacuoles surrounding the bacteria. The included bacteria 

 are destroyed bv ferments produced by the phagocyte. It is an 

 intracellular digestion. The length of time necessary for the 

 phagocvte to destroy the bacteria is variable. The bacterial 

 destruction mav be instantaneous or the bacteria mav possess 

 sufficient vitality to destroA' the phagocyte. There is consider- 

 able evidence that infection is frequently generalized in the ani- 

 mal body bv leucocytes that have enveloped bacteria and wan- 

 dered to another portion of the body. The included bacteria 

 destroy the leucocyte and, thus liberated, establish a new cen- 

 ter of infection. 



Phagocytosis is a very important factor in inflammation. 

 No doubt many localized inflammatory conditions are aborted 

 and the intensity of the attack of other infective inflamma- 

 tory conditions reduced bv the process of phagocytosis. There 

 is a peculiar variation of phagocytosis occasionally observed, 



