12(; 



which was shiiiu'd pink, apj)t'ai-c'{| IJic epithelium stained 

 yellow-greenish. In parts oi the culture the epithelium 

 had formed a glanil-likc structure. Several tubules could 

 be seen with distinct luniina surrounded by a regular high 

 epitlu'Hum. llu- nuclei were all located near the basal 

 membrane. Some of the lumina were filled with a colloidal 

 secretion and stained yellow. It is worth noticing that the 

 Van Giesons stain does not differentiate between epithe- 

 liiiin And rihi'oblasl wlicn the culture is stained as a whole, 

 only in sections. I'lu' plasma clot seems to prevent the dif- 

 ferential staining. 



This experiment shows clearly that the two strains of 

 cells remain definite by being cultivated in vitro and it 

 shows also that the epithelium has a definite formative 

 ability. C h a m p y i-") has stated that epithelium does not 

 dedifferentiate when connective tissue is present. In our 

 experiments we mixed tw^o strains of tissue cells, which 

 had been cultivated in vitro for a long period of time, 

 and should have dedifferentiated a long time ago after the 

 assumption of C h a m p y 127) 'f^g chemical difference of 

 the cytoplasm of epithelium and connective tissue gives 

 us, by using Van G i e s o n's stain, a beautiful test for the 

 presence of the two cell tj^pes. 



Now since it is a fact that we do not have any dedif- 

 ferentiation or transformation of epitlielium in vitro, pos- 

 siljililic's are opened up for new investigation of the interac- 

 tions of the two kinds of cells. It would be of the greatest 

 interest first to find out if there is any difference in the 

 most favourable conditions for growth of the tw^o cell types 

 in vitro. 



There seems to be one main difference, at least, between 

 the epithelial cells and the connective tissue cells, and that 

 is their behavior to the stroma. The epithelial cells follow 

 the way of least resistance to a greater extent than do the 

 fibroblasts. The individual fibroblasts are able to penetrate 

 through a dense meshwork of fibrin without any difficulty. 



