90 Society for Experimental Biology and Medicine. 



quantity of turpentine is injected into the pleural cavity, there is 

 abundant exudation of coagulable fluid and the serous surfaces 

 are covered by thick layers of fibrin. Accumulation of fluid which 

 can be followed during life by percussion of the animal's chest 

 reaches a maximum at the end of three days, and then gradually 

 subsides so that at the end of six days, in most instances, the 

 cavity contains no fluid. Fibrin, though diminished in amount, is 

 still present, and gradually disappears, so that at the end of two or 

 three weeks, the cavity has returned to the normal, save for a few 

 organized adhesions. 



During the early stage of the inflammation, fibrinous exudate, 

 freed from the serum by washing in salt solution, undergoes diges- 

 tion when suspended in an alkaline (0.2 per cent, sodium carbonate) 

 or in an acid medium (0.2 per cent, acetic acid). At the end of 

 six days, at a time when fluid has disappeared from the pleural 

 cavity, digestion fails to occur in an alkaline medium, but occurs 

 with great activity in the presence of acid. 



During the first stage of the inflammatory reaction, when fluid 

 is abundant and the fibrin which is present digests in the presence 

 of alkali, polynuclear leucocytes are very numerous in the meshes 

 of the fibrin. In the second stage, when fluid has in great part 

 disappeared, and the fibrin contains only one enzyme digesting in 

 the presence of acid, polynuclear leucocytes have disappeared and 

 only mononuclear cells are embedded in the fibrin. 



Since the acids, which, in vitro, favor the action of the enzyme 

 present in the second stage of the process, do not occur in the 

 body, the possibility has suggested itself that carbon dioxide brings 

 this enzyme into action. If carbon dioxide is passed through 

 normal salt solution in which strips of such fibrin are suspended, 

 digestion is very greatly hastened. The normal inhibition exerted 

 by blood serum upon the enzyme is overcome by carbon dioxide ; 

 in the presence of a small quantity of blood serum, carbon dioxide 

 causes greater enzymotic activity than in the presence of salt solu- 

 tion alone. 



