112 



INFLAMMATION. 



that it has undergone a change as it passed. The way in which this 

 alteration in the composition of the blood plasma occurs as it passes 

 through the walls of the vessels and becomes the seruni of exudation, we 

 do not understand. But it is probably due 

 to metabolic processes in the endothelial 

 cells by which what has been called a "se- 

 lective filtration " is secured. 



The fluid exudate contains fibriuogenous 

 substance, and from this, when the condi- 

 tions are favorable, fibrin may be formed 

 (Fig. 38) by a change similar to that which 

 occurs in the coagulation of the blood. The 

 leucocytes which wander into the tissue 

 spaces outside the vessels may encounter 



conditions inimical to life, from innutrition or from the presence of dele- 

 terious substances, and thus these and other cells furnish as they die and 

 disintegrate the fibrin ferment essential to coagulation. Clusters of 

 fibrin fibrils may thus often be seen surrounding dead and disintegrat- 

 ing cells (see Fig. 39). ' 



If at this time the exposed bladder or mesentery of the frog be re- 

 stored to the abdominal cavity and the animal placed under favorable 

 conditions, the reaction of the vessels and cells to the unusual environ- 

 ment may, if the injury have not been too severe, gradually subside. 

 The circulation is then re-established, the serum is absorbed, the leuco- 

 cytes which have not come out upon the surface or died in the tissue 



FIG. 38. FIBRIN IN INFLAMMATORY 

 EXUDATE. 



FIG. 39. FIBRIN FORMING AROUND DEAD CELLS IN THE INTERSTICES OF TISSUE. 



spaces may re-enter the lymphatics. Fibrin, if this have been formed, 

 and red blood cells which have escaped from the circulation are dis- 

 posed of by simple decomposition, or under the influence of ferments 



1 For a discussion of the relationship of fibrin formation to cells which may furnish 

 a substance inducing coagulation see Hnuser, Virch. Arch., Bd. cliv., p. 335, 1898; also 

 Arnold, Cbl. f. Path., Bd. x., p. 313, 1899. 



