WOUNDS 89 



Proud flesh is merely a mass of profuse granulations, and in- 

 dicates either a lack of vitality or else external irritation. The 

 latter is usually caused by germs. 



Development of new blood vessels.— New blood vessels de- 

 velop from vessels that previously existed in the injured tissue. 

 The growth of new blood vessels and new tissue for union start 

 together and continue until enough granulation tissue has been 

 developed to fill the wound gap. The new vessels start by 

 budding from capillaries near the surface, and are always short. 

 These buds project farther and farther and gradually change 

 into threads, which gradually hollow into tubes, beginning at 

 the end near the old capillary. It happens frequently that the 

 ends of two neighboring projections meet and unite to form an 

 arch. As this becomes hollowed out, a capillary loop is formed. 

 When the development is complete, then new blood vessels may 

 start from this one and perhaps develop another arch. The 

 thread-like projections are probably hollowed out by tne blood 

 current in the parent vessel. 



Granulation tissue in the beginning is more vascular than 

 normal tissue, in fact, largely a tuft of capillaries. Useless 

 vessels are constricted and finally obliterated. 



Inflammation in wounds is due to foreign material; for in- 

 stance, dead tissue or foreign bodies, but more commonly to 

 germs which, by multiplication, give rise to wound infection 

 and inflammation. 



Osseous tissue. — Wounds in bone tissue heal in the same way 

 as those in other tissues, the wound surface being covered with 

 granulations. The development of new tissue is from the perios- 

 teum and from the marrow at the place of injury. At the 

 end of a few weeks, the ends are united by a spongy mass be- 

 neath the periosteum and in the medullary canal. This mass, 

 called a callus, gradually becomes organized, and later, is partly 

 removed. 



Cartilage. — On account of low nutrition cartilage has very 

 little power of repair. Loss of cartilage is generally repaired by 

 fibrous connective tissue. 



Nerve tissue. — After a nerve is cut, the severed portion de- 

 generates. New axis cylinders come down from the stump and 

 grow through or along old sheaths of the severed portion. It 

 is doubtful whether primary union ever takes place. Quick 

 return of sensibility does not necessarily imply restoration of 



