108 



that the cells iwc \)\]vv nnd Mini no dcditlVrcnlinlioii lins 

 taken placo. 



I\|)illu-liuni has liccn ciillivnlcd IVoni luinian Ix-ini^s. dogs, 

 cals, chickins and I'roni scxcral cold l)loodcd animals H u I h 

 '"I), Op pel '•'. Holmes-''', l' li I e ii h u I li '■'') and (bar- 

 rel Carrel* has ollen li'ied to obtain j)ermanent strains 

 of cpillu'lium as is done with connective tissne cells, bnt 

 alter cullivalion lor a certain length ol' time the epithelial 

 cells disappeared and fibroblasts began to appear. This in- 

 vasion of fibroblasts was due to a contamination of the 

 epithelial cells with fibroblasts from tiie very beginning at 

 the time of exjjlanlation. It may have only been an apparent 

 appearance of fibroblasts, 1. e.. a morphological change of 

 the polygonal epithelial cells into a fibroblast-like type of 

 sjiindle cells may have taken place. Champyi^s) inter 

 preted the i)henomenon as a dedifferentiation. Uhlenhuth 

 *3S) i'xj)lained the dedifferentiation as the results of the me- 

 chanical conditions of the culture medium. 



TECHXigUE FOR THE PREPARATION OF THE TISSUE. 

 The epithelium for the cultivation is obtained from that 

 part of the iris which spontaneously adheres to the brim 

 of the lens when it is removed. The lens is profitably taken 

 from the eye of the 10—12 days old chicken embryo. The 

 best way of extracting the lens, is to make a slight inscision 

 in the |)osterior pole of the eyebulb and with a small for- 

 ceps, the entire corpus vitreum is drawn out. Atta- 

 ched to the front of the corpus vitreum the lens will be 

 found. The lens is now separated from the corpus vi- 

 treum. In most cases a thin black brim of the iris will be 

 found on the lens. It is necessary to work on a l)ackground 

 of some white ])aper or so, otherwise the black iris brim will 

 not be seen. The lens is cut in 2 oi' 1 pieces and placed 



*) Carrel, A., unpublislied experiments. 



