102 THE GERM THEORY OF DISEASE. 



presence. If, however, the substance is too difficult of diges- 

 tion, over-stimulation results, and instead of the soluble fer- 

 ment being formed, the cells degenerate, pus forms, and the 

 process fails. 



DIGESTION OF SPONGE. 



Let us examine the operation of the sponge graft. In the 

 sponge, as prepared for this operation, we have a material 

 somewhat difficult of digestion, a material that would be very 

 slowly acted upon by the gastric juice. From this circum- 

 stance, and the fact of its very minute porosity, it has, hap- 

 pily, been selected for the purpose of inducing granulations 

 for the filling out of lost tissues. What may have led to this 

 selection I am not informed. It was probably directed by 

 some accidental observation. The fact, however, is now well 

 established, that the tissues are stimulated, by its presence, to 

 fill its pores with granulations, after which the sponge itself 

 gradually disappears, leaving the opening filled with new 

 tissue. 



The physiological phenomena may be thus explained : as 

 lias been said, the tissue is stimulated by the presence of the 

 sponge, and granulation proceeds actively. At the same time 

 a soluble ferment is thrown out, by whicli those portions of 

 sponge inclosed in the matrix of granulations are slowly di- 

 gested and pass off by osmosis. At the same time, the granu- 

 lations crowd into the space gainec}. This process continues 

 regularly, until every particle of the sponge is removed, and 

 its place supplied by living tissue. I think it will be clear to 

 every one, especially to every surgeon, that this sponge does 

 not dissolve in the ordinary plasma of the blood, or tissues. 

 The tissues are stimulated to an extraordinary proliferation of 

 cells by its presence. They are also stimulated to the secre- 

 tion of a soluble ferment, suitable for its digestion and re- 

 moval. 



