Chap. 7 TISSUES 125 



cells. In the walls of adjoining blood vessels, cells (endothelial) multiply 

 and form branches which extend into the scar tissue, their presence account- 

 ing for the "red scar." By this time the surface of the scar is covered by 

 epithelium. Contraction of the white fibers reduces the capillaries and the 

 "white scar" results. 



Bruises. Such bruises as a black eye are produced by blunt objects which 

 crush blood capillaries and other tissues. The capillaries bleed; the hemoglobin 

 of the accumulated blood breaks down, causes the black and blue and later 

 the greenish colors. 



Fever. There may be a general response to injury in a fever involving the 

 whole body. It results in an increase of metabolic activity and a consequent 

 rise in temperature. High temperature is a dependable sign that something 

 unusual is going on in the cells of the body. 



Hypertrophy. The enlargement or hypertrophy of a particular region or 

 organ may be due to enlargement, i.e., hypertrophy of individual cells and/or 

 increased number of cells, i.e., hyperplasia. If one kidney has been removed, 

 the other usually enlarges with more cells and does extra work. 



Atrophy. This is a degenerative process in which cells diminish in size 

 and number. It is sometimes due to lack of blood or nervous control. A com- 

 mon example is the degeneration in leg muscles following the destruction of 

 parts of the nerve cord in infantile paralysis. 



