We have already seen that an acute pleurisy may result in adhesion of the sac, the process of adhesion resulting from coalescence of the surfaces which have become like granulation tissue from the inflammation. Such adhesion will not occur so long as fibrine is present on the surface, and is to be carefully distinguished from the mere glueing which may occur in the earlier stages from the adhesion of the fibrinous exudation on opposed surfaces. We have also seen that in the frequent chronic pleurisy of phthisis a similar adhesion occurs, and the method of its occurrence is similar. Without any fibrinous or serous exudation the surfaces come to have the characters of granulation tissue, and coalescence with vascular communication occurs.