FIBROU,S TISSUE rRODUCED AS A REACTION TO INJURY. 607 



vicinity, uor of any distension of the blood-spaces. The fact 

 that the vod ol: jelly was always itnplanted as fai* as possible 

 parallel to the long axes of the muscle-fibres, and that they 

 were usually rather separated from each othei', than cut by 

 the insertion of the transplanting needle, probably contributed 

 towards this result. 



After a period of about seven to eight days there were 

 signs of division of the fibroblasts in the neighbourhood of 

 the implauted mass, and a slow migration of the new-formed 

 cells towards the agar took place. By about the tenth diiy 

 these cells had arranged themselves so as to form a tliin and 

 delicate ensheathing layer. The process presents marked 

 differences from that which occurs after the implantation of 

 a substance which causes an inflammatory reaction, with the 

 consequent development of a protecting layer of agglutinated 

 corpuscles. The division of the fibroblasts, instead of being- 

 rapid and amitotic, is comparatively slow, and frequently, 

 though not always, mitotic. The nuclei of the young fibro- 

 blasts retain their elongated shape, and though the nuclei of 

 the dividing cells lose their typical spindle-like appearance 

 and become oval, they do not become round, as in the case of 

 rapid division after inflammation. The layer of fibrous tissue 

 formed is thinner and less compact, the proportion of cyto- 

 plasm to nucleoplasm is greater, and the nuclei assume their 

 typical spindle shape more rapidly. The process seems to be 

 complete by the tenth day, and the appearance is almost 

 identical with that showji in fig. 5, which represents the 

 condition after seventeen days. 



In some of our experiments the sealing-wax with which the 

 drill holes were closed became detached in the tank. The 

 holes were re-sealed as soon as this was noticed, but the 

 animals seldom survived long. On sectioning, an area of 

 inflammation was usually found surrounding the agar, and 

 rapid division of the fibroblasts in the vicinity was in pro- 

 gress. In specimens that survived longer a complete sheath 

 of fibrous tissue had formed round the agar, and the con- 

 dition resembled that resulting from implantation of gill- 



