74 PATHOLOGY. 



has then changed to a mass of fibers distributed through the sur- 

 rounding connective tissue. The axis cylinders receive new 

 sheaths which probably grow from nerve cells lying within the 

 old sheaths. Whether the new fibers ever reach the old ter- 

 minals, depends upon the amount of intervening tissue and the 

 density of it. The limit of growth is placed at from one to 

 two inches. 



The new tissue. — In certain tissues, extensive injuries may 

 he repaired by tissue which completely resembles the original. 

 This is true of tendons and bones. Muscular tissue seems to 

 have much less ability to repair extensive injuries. Scar tissue 

 contracts for a long time after healing is complete. The scar 

 is large when there has been more granulation tissue than need- 

 ed or where an extensive removal of tissue necessitates a great 

 amount of scar tissue. Scar tissue in this case is endowed with 

 low vitality, and is poorly nourished. 



How skin recovers a surface. — A wound is not entirely healed 

 until it is recovered. This takes place by development of new 

 epithelial cells from preexisting ones of the skin. These new 

 epithelial cells gradually form new skin which grows from the 

 margin and has a slight bluish pink color. It only covers the 

 granulations loosely at first, but later unites firmlv to them. New 

 epithelial cells have the power of amoeboid movement. They may 

 become detached from the margin and set up a new covering 

 center elsewhere on the wound surface. Restoration of the skin 

 surfaces and for that matter the entire healing is favored by sur- 

 gical cleanliness, and is hindered by irritating medicines, and by 

 rubbing sponges, etc., over the surface. 



An exception should be noted, viz., that when healing has 

 ceased in case of an old sore, with the surface not yet covered 

 by skin, healing may sometimes be given a vigorous start by a 

 blister. 



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