II THE STIMULUS FOR WOUND HEALING 669 



ical bonds (templates) produced at adjacent surfaces by the interlocking of 

 macromolecules, similar to the lock-and-key theory of the antigen-antibody 

 complex. 



Epithelial growth would serve as a good example of the "coaptation" theory. 

 In a one-cell layer each cell has specific coaptic relationships: laterally, the cell 

 is in contact with an identical cell type; beneath, it is related to a basement mem- 

 brane and the underlying dermal cells; above, it is in contact with the external 

 environment. If the epithelium is damaged, those cells at the wound edge have a 

 laterally exposed surface. The cell valences (of the template) on the exposed 

 surface are unsaturated, and migration ensues. Movement continues until 

 apposition is again established with a similar cell type. Upon contact, the lateral 

 valences again become saturated and stability is restored. Chiakulas (1952) found 

 that grafted flank epidermis in Amblystoma opacum and Triturus torosus fused equally 

 well with epidermis from the tail, fin, fore-and-hind limbs, cornea, jaw, or head. 

 Cells of endodermal origin, which normally are in coaptive relationship with the 

 oral lining, also fused with the skin, however, gut and gall bladder epithelium 

 were not compatible. Compatibility was manifested by a cessation of movement 

 and fusion of the newly opposed edges. When incompatibility occurred the mi- 

 grating epithelium either continued to move over the opposing edge or else the 

 cells piled up and failed to fuse; hence, epithelial cells, even when transplanted, 

 retained their type specificity and the ability to "distinguish" beween related 

 and unrelated cell types. Further discussion of this concept as related to mammalian 

 healing is presented under the section on epithelialization. 



III. W^OUND CLOSURE 



There are essentially three processes by which wounds close: (i) contracture, 

 (2) intussusceptive growth, and (3) growth from the wound edge. The role that 

 each of these plays varies according to species and more particularly to the area 

 of body surface involved. 



{a) Contracture 



Carrel (1910) was one of the first to study the influence of contracture on wound 

 healing although this phenomenon had already been recognized earlier (Spallan- 

 zani, 1787; Born, 1897; Minervini, 1904). In wovmds on the trunk of dogs, 

 cats, and guinea pigs, where skin is mobile, he found contraction was the pri- 

 mary method of closure. Loeb (1920) concluded from studies on guinea pig ear 

 wounds, where skin is non-mobile, that closure was chiefly effected by epitheliali- 

 zation. The distinction between healing in mobile and non-mobile skin was 

 postulated by Burrows (1924): mobile skin, characterized by a well developed 

 layer of subdermal muscles (panniculus carnosus), e.g. the rat and guinea pig, 

 heals chiefly by contraction. The initial granulation tissue and its overlying 

 migrated epithelium have merely a temporary function and ultimately disappear. 

 In non-mobile skin, contracture is minimal and granulation tissue is converted to 

 a fibrous scar covered with epithelium. 



Lilerature p. yo3 



