140 



Scientific Proceedings (92). 



may heal, only to form again, in case the wire should continue to 

 irritate the skin. 



Microscopically we find in the rat in the first stage, that of 

 ulceration, the base of the ulcer formed by fibrous or hyaline tissue 

 which is infiltrated by fibroblasts. The wire is seen lying at the 

 base of the ulcer surrounded by necrotic tissue and polynuclear 

 leucocytes. On the whole, the capillaries run radially towards 

 the surface of the ulcer, while the fibrous tissue and the fibroblasts 

 are arranged in a direction more or less parallel to the surface of 

 the ulcer. At the side of the ulcer near the tip of the regenerating 

 epithelium, the growing connective tissue is more cellular and less 

 fibrous and the capillaries are more dilated and a greater influx of 

 polynuclear leucocytes is observed than at the base of the ulcer; 

 at the latter place the pressure is greater and this may be respon- 

 sible for the greater production of dense fibrous tissue and the 

 poorer development of capillaries. 



In cases in which the wire healed in we find it in later periods 

 embedded in a canal which is surrounded by a small zone of nec- 

 rotic tissue and polynuclear leucocytes. This zone is followed by 

 an area of dense fibrous tissue, surrounding the wire on the whole 

 more or less concentrically (although some deviations may occur), 

 while the capillaries run more or less in a radial direction towards 

 the wire; however, at some places they may adapt themselves to 

 the concentric course of the fibrous tissue. Certain deviations 

 from this arrangement seem to occur. Mechanical factors, 

 pressure and pull, and a stereotropic reaction, determine probably 

 essentially the direction in which the fibroblasts are arranged, 

 and pressure as well as certain chemical factors cause probably 

 the transformation of the fibroblastic into fibrous tissue. 



The blood capillaries evidently do not respond to the same 

 degree to the mechanical factors which determine the movements 

 of the fibroblasts; they often run in a direction approximately 

 radially to the lines of pressure and often continue to follow this 

 direction at a time when the connective tissue has assumed an 

 arrangement parallel to the lines of pressure and at right angles to 

 the blood vessels. We may point out that from a teleological 

 point of view, the difference in the reaction of connective tissue 

 and capillaries appears as a useful adaptation to the requirements 



