EPITHELIUM OF THE CORNEA. 427 



The expanded basal borders of the cells are so applied to 

 each other, or are so superimposed upon one another by their 

 thin edges, that the borders of the several cells seen collectively 

 in situ make a bright stria which forms the line of demarcation 

 between the epithelium and the corneal tissue. Henle* men- 

 tions this stria, but gives another interpretation of it. 



I have satisfied myself, as regards Man and Mammals, that 

 the stria is due to the basal borders of the innermost cells. 



An accurate knowledge of the normal condition of the dif- 

 ferent layers of the corneal epithelium is so much the more 

 requisite, as this epithelium plays an important role in the 

 investigations that have recently been made in regard to 

 epithelial regeneration. 



J. Arnold, t who began the investigation, it is well known advanced a 

 proposition of quite fundamental importance in admitting that the new 

 epithelium filling an artificially produced abrasion of the epithelium 

 arises from a blastema formed in the hollow. This, he thought, be- 

 came converted at the border of the space into hyaline protoplasm, which 

 divides into portions containing nuclei, i.e. into cells. The experiments 

 on the external epithelium of the cornea made by Wadsworth and Eberth,;]; 

 F. A. Hoffman and Heiberg,|| are however collectively opposed to the 

 existence of Arnold's blastema. The regeneration occurs through the 

 agency of daughter cells that arise by germination and fission of the 

 epithelial cells forming the border of the cavity, or from the marginal 

 cells of epithelial islands remaining intact in the cavity. 



F. A. HoffmanlF states that he never observed processes in the cells of 

 the lowermost epithelial layers. This would indicate that the last-named 

 layer had a definite position (see Cleland** and Krause).ff Heiberg,JJ 

 however, opposes Hoffman's statements. But Heiberg lays too little 

 stress on the peculiarity of the intact lowermost cell layer of the 



* Henle, loc. cit., p. 605, fig. 459. 

 f Virchow's Archiv, Band xlvi. , p. 168. 

 t Virchow's Archiv, Band li., p. 361. 

 Virchow's Archiv, Bandli., p. 373. 



|| Medicinische JaJirbiicher der Gesellschaft der Aerzte in Wien, Jahrgang, 

 1871, p. 7. 



IF Hoffman, loc. cit., pp. 388 and 389. 

 ** Cleland, loc. cit, p. 363. 

 ft Krause, loc. cit., p. 235. 

 U Heiberg, loc. cit., p. 19. 



