120 



Willi Al'lci- llic ciillivalion of cpillu'liiiiii Tor a corlain Icnirlh 

 of lime embedded in Hie clol. Ilie ^rowlli can suddenly 

 sel in will) ^i-eal inleiisil\ The i^rowlli is llieii \('i-v regular 

 and exii'nsive. The cells lorn) a nienihrane. usually con- 

 sisting ol" one layer ol" cells, but llie individual cells arc no 

 longer polygonal, bul spindle-sliaped b'ig. l<i. 17 Slill Ibis 

 picture does no! reseiid)le a cullnre of ril)rol)lasts. The cells 

 are closei\ in contact wiili cacb otber; tbeir protoplasm 

 is sprt-ad out and gives the a|)pearancc ol" I'lat cells. In the 

 peri|)herv of such i culture we siiall very rarely find a 

 lU'lwork as in Hie fibroblasts cullin'c; bul we sball see 

 smaller or lai'gcr longue-like pi'ocesses consisting of many 

 cells in close relation to eacli olher. which practically is 

 never b»und in tlie connecliNc tissue cultures. ^\ lien we 

 have this type of culture, fusiform epithelial cells growing 

 in Ilie clot and |)ro(lucing e\-en a membrane-like grow'th 

 of ni'w cells all around, we liave a lyi)e of epithelial cells 

 which is found to grow veiw !"apidl,\. An illustration of 

 this ly|)e can be seen in b'ig. 10 and 17 



Hesides this ra|)i(lly growing type of epithelial cells, we 

 have llu- one which, gr'ows in winding tubules big. M). This 

 lyi)e grows very slowly and irregularly. The tubules or solid 

 processes protruding from Ihe clot m.i\ be long and thin 

 or shorl and Ihick. These tubules are often very peculiar, 

 that is. they are very sliglhlly refractive, so that they can 

 scarcely be distinguished in the mici-oscope Sections inade 

 on such cultures may show tubules with a distinct lumen; 

 sometimes we have only a single layei" of cells around 

 the lumen, and sometimes we can see sevei'al layers. At 

 other times we have no tubules, but solid epithelial pro- 

 cesses. 



Fig. 18 shows such epithelial peninsulas shooting 

 out from the tissue fragment. These look very similar to 

 the solid processes of inv.a(ling epithelium we know from 

 certain carcinomata at tlie line of deniarkalion between 

 carsinomatous and normal tissue. HeciMillv tlieiv has been 



