546 SHINICHI MATSUMOTO 



Several papers have already appeared which deal with the 

 movement of epithelium of various kinds in vitro (Ruth, '11, 

 Champy, '14, Loeb, '02, Osowski, '14, and others). The observa- 

 tion of frog skin in vitro has been described by Holmes ('14) and 

 Uhlenhuth ('14) recently in detail. Previous to this, Harrison 

 ('10) Carrel and Burrows ('11), Lambert and Hanes ('13), and 

 others mentioned it briefly in their papers on tissue culture. 

 Among the w^orks which deal with the culture of the corneal 

 epithelium, that of Oppel ('12), who made use of the cornea of 

 certain warm-blooded animals in his investigations, demands 

 special attention. Harde ('16) made brief mention of an active 

 lateral spreading of the corneal epithelium in the culture of vac- 

 cinia with corneal tissue. However, the materials which were 

 used by Oppel and Harde are evidently not very suitable for 

 direct observation. For this purpose cornea of more simple 

 structure is desirable. It must be added that a number of investi- 

 gations on the problem of the wound healing of the cornea have 

 been made, such as those of Peters ('85), Salzer ('11), Lowenstein 

 ('13), and others, which must, of course, be taken into considera- 

 tion. 



I. BEHAVIOR OF EPITHELIUM CULTIVATED IN VITRO 



The cornea of the adult frog (especially R. pipiens) was used. 

 After thoroughly washing its whole surface with sterilized 

 Ringer's solution by means of a pipette, the entire cornea was cut 

 out with a razor and put into Ringer's solution (or serum), after 

 which it was divided into small pieces with very sharp scissors 

 so that the fragments showed sharp edges. Pieces cut radially 

 were preferred. 



The cultures were all made by the hanging-drop method 

 (Harrison, '10), the technique of which need not be detailed here. 

 The piece of cornea was taken from the Ringer's solution and 

 dropped on the surface of the cover-glass ; excess solution was re- 

 moved and a drop of plasma (or serum) run over the fragment ; 

 autoplasma was used in most of the cultures. The cover-glass 

 was then inverted upon a thin glass ring and sealed on with 

 vaselin (Harrison, '14). 



