I'MP.ROUS TISSUK rUoDliCKl) AS A REACTION TO INJLIEY. 603 



sniiiller size, iire easily (listinguislied fi-oin the blood-corpuscles 

 (fig-s. 2 and 3). These fibroblasts largely follow the course of 

 the strands of fibrous tissue bounding the blood-spaces, and 

 they a]ipear to travel along in the spaces, being most plentiful 

 near the walls. At the same time, when they multiply very 

 rapidly, many migrate in all directions between the muscular 

 fibres towards the implanted tissue, and are not confined to 

 travelling only in the proximity of pre-existing connective- 

 tissue strands. 



Onreachingthe degeueratinglayerof agglutinated corpuscles 

 surrounding the implanted tissue, they arrange themselves in 

 rows, and their nuclei elongate in such a direction that their 

 long axes form arcs of a circle surrounding the implanted 

 tissue. Some fibroblasts penetrate among the degenerating 

 cells of the gill-tissue, which are being removed by phago- 

 cytes, and in this position start the formation of fibrous 

 tissue. 



The surrounding layer of fibroblasts gradually thickens, 

 and presents a somewhat stratified appearance. At first this 

 layer contains a number of blood-corpuscles, but these even- 

 tually are removed, probably by autolysis, leaving only the 

 fibroblasts, which can now be seen to be connected with each 

 other by numerous fine processes of the cytoplasm, the whole 

 presenting a somewhat reticulated appearance. In time this 

 tissue becomes more compact, and the reticulation vanishes. 

 It would appear that this has been caused by the conti'action 

 of the processes of the fibroblasts, with consequent approxi- 

 mation of the cells. Finally, the nuclei become long and 

 spindle-shaped, the amount of cytoplasm slightly increases, 

 and a layer i-esembling normal fibrous tissue results. 



In our experiments the great variation in the rapidity with 

 which the various changes described took place was very 

 noticeable. The health of the animal after the experiment 

 seems an important factor in accounting for this, for the slow 

 rate of fibrous tissue formation in unhealthy, as compared 

 with healthy animals, was very marked. 



Unfortunately none of the animals into which gill-tissue 



