202 



EPITHELIAL CAECINOMATA. 



itself is a reliable one, and sheds miicli light on the way in which 

 certain kinds of cancer penetrate into and extend through the 

 parenchyma of organs. With this part of Kbster's theory, the in- 

 dependent growth of the epithelial sprouts asserted to take place 

 by Thiersch may very well be reconciled. It is only the addi- 

 tive growth by metamorphosis of the lymphatic endothelia, 

 which is radically incompatible with TJuet-sdCs views. I have 

 always warned my hearers against the danger of adopting a 



Fig. 64. 



/|^B^k^i|^J\ 



Horizontal section through tlic proliferating zone of an epi- 

 thelial cancer of the skin. Extension of the epithelial pro- 

 trusions along the interior of the lymphatic ycssqIs. After 

 Kuster. 



one-sided conclusion on this matter, and I do not even now see 

 any reason for deserting the via media Avhich I have hitherto 

 followed. In epithelium (as eg. also in cartilage) I distinguish 

 between a primary and a secondary mode of growth ; the former 

 consisting in the addition of young and small cells at the junc- 

 tion of the epithelium with the connective tissue, the latter in an 

 enlargement and proliferation of the cells in the middle of the 

 epithelial layer. To the former of these two factors is due the 

 growth in length and breadth, to the latter the sudden condensa- 

 tion of the young stratum which is familiar to every microscopist. 

 (Cf the skinning over of raw surfaces, fig. 39). The pheno- 

 mena are the same in disease. The actual extension of the epi- 

 thelial sprouts is due to the apposition of mobile cells derived from 

 the nutrient apparatus (according to Kdsttr of proliferated 

 endothelia) to their most advanced points. Their subsequent 



