COMPOSITION OF PUS 277 



esses: (1) Necrosis of cells; (2) local accumulatiou of leucocytes; 

 (3) digestion of the necrotic cells, fibrin, and tissue elements by en- 

 zymes which are derived from three sources, as follows: (a) the 

 leucocytes; (&) the infecting bacteria (if such are present) ; (c) the 

 fixed tissue-cells. Possibly small quantities of enzymes are also intro- 

 duced in the blood plasma, but these are probably very inconsiderable. 

 Normal serum, and probably also normal cells, contain antibodies for 

 the proteolytic enzymes of the leucocytes, and hence neutralization or 

 destruction of these antibodies must be an important factor in de- 

 termining the rate and amount of suppuration.*'^ 



The influence of the antienz^nnes is well shown by the rabbit, with 

 serum rich in antienzymes and leucocytes i)oor in protease, so that 

 infections with pus cocci do not usually lead to the formation of liquid 

 pus (Oine). In man we see a similar relation, in that exvidates rich 

 in serum do not suppurate because the enzymes are inliibited by the 

 senim ; but if the excess of serum is removed suppuration may then 

 occur. AVith an excess of enzyme (i. e., leucocytes) the inhibiting 

 effect may also be overcome, and suppuration then begins. Variations 

 in the proportion of leucoprotease and serum antiprotease determine, 

 therefore, the occurrence of suppuration, and the inflammatory re- 

 action is seen to be fundamentally the same as the humoral reactions 

 of immunity, in that in each case the essential process is the provision 

 of proteolytic enzymes to remove foreign or abnormal protein sub- 

 stances. In inflammation the proteolytic enzymes are brought in the 

 leucocytes, in humoral reactions the enzymes are present free in the 

 plasma. The antiproteases may be of the nature of lipoids, probably 

 with unsaturated fatty acids (Jobling). 



The proteolytic enzymes of the leucocytes and tissue-cells have been 

 previously considered in connection with the subject of autolysis 

 (Chap, iii), and it is necessary here only to call attention to the fact 

 that these enzymes are of at least two varieties: (1) Proteolytic 

 enzymes of the polymorphonuclear leucocytes, which act best in alka- 

 line medium (Opie ^^) ; (2) autolytic enzymes of the tissue-cells, which 

 act best in an acid medium (Hedin, et al.) . The mononuclear leuco- 

 cytes contain, like the tissue-cells, enzymes acting in an acid medium. 

 The antienzymatic action of serum is favored by an alkaline reaction, 

 but is altogether lost in an acid medium (Opie). 



COMPOSITION OF PUS 



Because of its method of production, pus consists of the follow- 

 ing substances: (1) The constituents of the exuded blood plasma; 

 (2) the constituents of the leucocytes (and tissue-cells) that exist free 

 in the pus; (3) the products of digestion of the proteins of the leuco- 



67 See Opie, Jour. Exper. Med., 1905 (7), 316; 1907 (9), 207; Arch. Int. Med., 

 1910 (5), 541. 



68 Jour. Exper. Med., 1906 (8), 410. 



