480 Mr. A. J. Walton. On the Variation in the 



In the majority of cases only a few branching connective tissue cells were 

 visible, and they extended only for a short distance into the surrounding 

 plasma, the difference between the amount of connective tissue growth in 

 young and old plasma being very marked (fig. 2). 



(c) Old Tissues Growing in Old Plasma. — In this group there was a 

 moderate amount of growth, about 80 per cent, of the cultivations being 

 successful. In every experiment some of the specimens showed good 

 growth. On comparison, however, it was always seen that this growth 

 was less than when young tissues were used. 



In the case of the thyroid a few cuboidal cells were seen growing from 

 the edge of the tissue after about 48 hours, growth being present in 70 per 

 cent, of the specimens. After a further 24 hours connective tissue cells were 

 visible. It was found in the parallel series that not only was growth more 

 extensive when young tissue was used both as regards the parenchymatous 

 and connective tissue cells, but that a larger percentage of specimens showed 

 activity. 



"With the liver good results were obtained, the characters of the growth 

 corresponding with that described in previous communications.* In this 

 series growth took place in 88 per cent, of the specimens, and when present 

 there were always to be seen masses of deeply staining cuboidal cells, but 

 these masses were always less marked than when young tissue was grown 

 in the same plasma. Proliferation of connective tissue cells took place at a 

 slightly later date, the cells soon growing beyond and between the masses of 

 parenchymatous cells. Here again the zone of connective tissue growth was 

 always less marked than was the case with young tissue (fig. 3). 



(d) Old Tissue Growing in Young Plasma. — This was found to be the worst 

 combination. The tissues apparently were not so active and the medium was 

 less suitable. In the majority of cases no growth took place. The tissues 

 stained poorly and apparently died. 



In the case of the thyroid only 3 per cent, of the specimens showed any 

 growth at all, and even in the successful cases this was extremely slight. In 

 the majority, even at the end of three or four days, the edge of the tissue 

 remained sharply cut. In some the plasma was liquefied, but in others this 

 change had not taken place, so that here again the absence of the growth was 

 not dependent upon a mechanical factor. Even in the few cases where there 

 was any evidence of growth, no cuboidal cells could be seen. At most there 

 were one or two elongated connective tissue cells to be found after a careful 

 search, so that at first sight there was a tendency to believe that no growth 

 had taken place. 



* ' The Journal of Pathology and Bacteriology,' vol. 18, p. 319 (1914). 



