li)2 



cpillu'lia! ci'lls. culliN ;iU'(l on llic Ircc sui-racc ol' llu' clol, 

 grew ill ti single layer and were tlescrihed as organizing 

 lheinsi>l\-es in slriielures which closely resembled ci-oss sec- 

 lions ol" glands. The expi-iinienls jiisl inenlioned conrinii 

 this slaleiiienl, since Ihe luhular arraiigenuiil may he I'ol- 

 lowed Ihroiighoul all serial seclions. 



("hanipy i-'^ slates Ihal no strains ol lissue cells can 

 he culli\alt(l Toi" any itiiglh ol lime in xili'o wilhoul a cliange 

 occnrring in their morpiiology. I ha\e shown Ihal I'ihro- 

 blasls ant! ei)illielial cells may he cultivaled in ])nre cnllnrcs 

 for long ])eriods without deditferentialion. Therefore, in this 

 case il seems Dial ("hampys '-'' statement does not con- 

 firm the e\|)erimeiital data. On the other hand, he also 

 stales lliat ei)ithelial cells in Ihe presence of conneclive lis- 

 sue cells do not dedifferentiate. This fact is fully suhstan- 

 liated hy my work. The experimenls in which pure strains 

 of epithelium and fi])rohlasts were mixed and allowed to 

 grow logetlier in one cultiu'e. show clearly thai normal 

 epithelial cells are not able to amalgamate with normal 

 fibroblasts as would be the case with cancerous epilhelium. 

 The normal epithelial cells stick together because of a cer- 

 tain iiilerdej)endancy of the cells upon one anothei". If the 

 epithelial cells were able to obtain the growth promoting 

 princi])les from other cells than the epilhelial, in this case 

 the fibroblasts, the picture would probably have looked dif- 

 ferent (1 h 1 o p i n 1^^) has always noted also thai the epilhe- 

 lial cells wer(> absolutely distinctly se])arated from the fibro- 

 blasts. 



It was staled by (> h a m |) y i--^; thai epithelium from 

 embryos, cultivated in \itro. dedifferenlialed within a few 

 hours and adult lissue persisted for a long lime in cultures 

 without changing. It was also stated that the dediffei'entialion 

 of e|)ithelial cells was delayed or did not take i)lace at all, 

 when fibroblasts or conneclive tissue cells were ])resenl. 



The same stalemenl was made ([uite recently by Drew 

 ^^''). ]\v describes how a ])ure culture of ej)itlu'iium com- 



