308 



HISTOLOGY OF THE MORBID PROCESSES. 



When, as in the example originally chosen, the injury affects 

 tissues that are normally covered with epithelium, the cells of that 

 tissue proliferate at the edges of the granulations until a layer of 

 epithelium completely covering them is produced. The whole proc- 

 ess of repair comes to an end with the formation of a dense fibrous 

 tissue that is only slightly vascularized by thin-walled bloodvessels 

 and is poor in cells. This is the scar, composed of " cicatricial " 

 tissue (Fig. 273). Upon the skin it is covered with epithelium ; 



FIG. 273. 



Dense fibrous tissue, or cicatricial tissue resulting from pericarditis : a, fibrous tissue, almost 

 devoid of nuclei and vessels derived from granulation-tissue; 6, lumen of a small 

 remaining vessel; c, moderate round-cell infiltration in the deeper portion of the 

 fibrous tissue, resulting from an immigration of leucocytes, and, perhaps, also from a 

 slight irritative proliferation of the fixed cells of the tissue ; d, subpericardial adipose 

 tissue. 



but there are no papillae beneath this covering, and the epithelium 

 is as poorly nourished as the cicatricial tissue beneath it. 



The cells of higher function in the damaged part which have not 

 been irremediably injured pass through the changes that will pres- 

 ently be described in the section on regeneration. 



The course of a simple acute inflammation, as outlined above, 

 may be modified and complicated by a number of circumstances 

 to such an extent that these variations must be briefly described. 



1. The Healing of Fractures. When a bone is broken the rejuv- 



