16 



DR, G. THIN. 



whicli are not supposed to be attended with any special 

 difficulty. The layer of larger flat cells indicated by the silver 

 lines will be found on disintegrating the tissue by needles to 

 correspond to the surface which limits the penetration of the 

 silver in the instance above indicated. It may be taken, then, 

 as a fact that a silver solution may permeate through a tissue, 

 but be arrestedby tin epithelial layer in the depth or thickness 

 of the tissue. To associate the narrow and anastomosing 

 colourless linear spaces that permeate the substance of a silver 

 cornea with the cells of a similar nature seems justified when 

 it is considered that by potash solution there can be isolated 

 from the cornea multitudes of elongated, narrow cells, and 

 that in gold preparations of the mouse's cornea, and more 

 rarely in tlie cornea of the larger mammals, rows of similar 

 elongated cells can be traced, taking their departure from 

 layers of polygonal flat cells, and penetrating the interstices 

 of the tissue. 



In the mouse's cornea treated by gold the layers of flat 

 cells ca|Dable of demonstration are, in the author's expe- 

 rience, composed of smaller cells than the layers of larger 

 cells which are seen in silver preparations. 



In potash preparations cells corresponding to those of both 

 layers arc isolable. The smaller cells can be seen occasionally 

 in a healthy mouse's cornea treated by gold, but more readily 

 when the structure has been inflamed for a few hours before 

 the animal has been killed. 



In the cornea of a frog sealed np in aqueous humour the 

 author, in conjunction with Dr. Ewart, saw the elongated 

 narrow cells in situ covering the j^rimary bundles, applied, 

 therefore, to structures having a signification similar to the 

 darkly-stained bands in the silver-treated cartilage (see 

 Figs. 14 and 15). The unstained lines in the cartilage jire- 

 parations correspond to the rows of cells seen by them in the 

 cornea. When it is considered that elongated narrow cells, 

 similar to but shorter than most of those which are seen in 

 the cornea, exist in cartilage, the presumption becomes very- 

 strong that in the cartilage, as in the cornea, they invest the 

 narrow bands of tissue on which they lie, and that the un- 

 stained lines seen in section correspond to the cellular invest- 

 ment of the darkly stained cylinders of ground-substance into 

 which the silver solution has permeated. 



Recklinghausen's doctrine of Saft-kancilchen rests mainly 

 on the fact that in silver preparations communicating colour- 

 less spaces are seen in a dark ground, and the unstained 

 stellate spaces in the cornea have been regarded as peculiarly- 

 well adapted for its demonstration. Eecklinghausen, believing 



