702 WOUND HEALING 8 



far been isolated. More recently, Weiss has proposed that migration is linked to a 

 disturbance in cellular relationship, a concept which coincides with the presently 

 available facts and affords a fruitful field for further investigation. 



The source of cellular components for epithelialization is well known ; however, 

 considerable confusion still exists concerning the origin of granulation tissue. The 

 initial cell accumulation in the wound area is composed of phagocytes from the 

 vascular system. Whether or not they remain at the site and differentiate into 

 dermal elements is not known. Undoubtedly a large portion of the fibroblasts 

 arise from the depths of the wound and enter the area along with invading 

 capillary buds. Accurate evaluation of the role of various cells in the formation of 

 granulation tissue must await means to identify individual cells for a period con- 

 commitent with that of wound healing. 



Within the past decade the advent of reliable histochemical techniques sup- 

 ported by quantitative biochemical studies have made it evident that wound 

 healing must be considered in a new light. Prior to this time healing was divided 

 into a lag phase and subsequent period of fibroplasia. It is now known that 

 the so-called lag phase is extremely important and sets the stage for the multiple 

 series of events associated with clinical healing, in view of this, the term substrate 

 phase appears more applicable. The subsequent period of fibroplasia associated 

 with collagen formation has also proved a fruitful field for investigation. 



