105 



DEVELOPMENT OP EPITHELIUM, 



mutual flattening of adjacent cells often misleads the observer 

 into the belief that he has before him the results of fissiparous 

 multii^lication ; the even line of contact between two cells pre- 

 senting a deceptive likeness to a plane of division ; hence the 

 most conscientious vigilance on his part is in this matter in- 

 dispensable. On the other hand, it is probable for many 

 reasons that the young epithelium-cells spring from the con- 

 nective tissue. Burl:hardt was the first to indicate the top- 

 most laye]' of the connective tissue as the matrix of the epithelial 

 cells. When he described (in the year 1859) the way in which 

 lie believed the young cells to emerge from the connective tissue, 

 and to assume an upright attitude as the youngest of the epithe- 

 lial cells, many of his readers had scruples about accepting his 

 results. Since that time, the migration of connective-tissue cor- 

 puscles has been directly observed by v. Becldinghausen in the 

 cornea ; and this observation gives colour to the view that the 

 renew^al of the epithelial cells is operated by a migration of their 

 youngest elements from the connective tissue. The facts of morbid 

 histology, so far from being antagonistic to this view, furnish 

 many illustrations well adapted to shed light on the migratory 

 process. I will only refer the reader to the interesting observa- 



FiG. 3 



Transverse section through a dermal papilla surrounued by epider- 

 mis. Migratory corpuscles may be seen both m the connective 

 tissue and bet^veen the epithelial cells. After Pagensiecher. 



lions of Biesiadecki and Fagenstecher ; m 



cases of slight 



and 



