90 VETERINARY STUDIES 



the injured fibers. The newly grown axis cylinders receive 

 sheaths which probably grow from nerve cells lying within the 

 old sheaths. Whether the new fibers ever reach the old terminals 

 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 

 be repaired by tissue which closely resembles the original. This 

 is true of connective tissue, skin, tendons, and bones. Muscular 

 tissue seems to have much less ability to repair extensive in- 

 juries and repairs partly by connective tissue in place of the 

 original muscle. Scar tissue contracts for a long time after 

 healing is complete. The scar is large when there has been 

 more granulation tissue than necessary, as in foot wounds, 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 those of the skin. These new epithelial 

 cells gradually form new skin which grows from the margin. 

 It covers the granulations loosely at first, but later unites firmly 

 with them. New epithelial cells have the power of ameboid 

 movement. They may become detached from the margin and 

 set up a new covering center elsewhere on the wound surface; 

 in fact skin and other tissue cells may be kept alive a long time 

 under suitable conditions for transplanting. Restoration of the 

 skin surfaces, and for that matter the entire healing, is favored 

 by rest and surgical cleanliness, and is hindered by infection 

 and injurious bacterial products, poor nutrition, and irritating 

 medicines, and the rubbing of 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. 



Many of the preparations commonly used by stockmen do 

 much more harm than good. 



