242 PKOGEESS OF MICROSCOPICAL SCIENCE. 



from eacli side respectively meet in the centre, where they join. The 

 remaining sides of the quadrangle are formed hy a side view of these 

 various cells, where they have been detached from the adjoining ones 

 in the breaking down of the cornea mass. The coincidence between 

 the breadth of the long narrow cells and the fibrillary bundles of the 

 cornea-substance, as seen when prepared by the ordinary rnethods, is 

 evident, the continuous planes formed by their junction indicating 

 that they form layers between which it is enclosed. According to this 

 view, the ground-substance is everywhere encased in a sheath of 

 cellular elements. Bowman's corneal tubes I believe to include both 

 the straight canals described in the paper above referred to and the 

 spaces between the long cells widened by injection, chiefly the latter. 

 Although I have nothing to add to the description of the mode of pre- 

 paration which I have already given, I must- state that there are con- 

 ditions of success, as to the nature of which I have not yet come to a 

 definite conclusion. Sometimes the same solution, applied at the same 

 temperature to diiierent cornefe, succeeds in one and fails in another, 

 and sometimes a solution prepared with every precaution has failed to 

 afford me any result. The two essential conditions to success are 

 complete saturation and temperature. I have never succeeded with a 

 temperature above 120°, nor with one below 102°; and so sensitive is 

 the solution to moisture, that preparations sealed in it with asphalte 

 seldom keep longer than one or two days, except in very dry weather. 

 On a damp day I have known a successful preparation left on the 

 object-glass disappear in six hours. The corneal mass may be kept 

 unaltered for at least some weeks in the solution by running sealing- 

 wax round the stopper of the bottle. A perfectly successful prepara- 

 tion shows nothing but the cells. Unsuccessful preparations, especially 

 those prepared with too hot solution, show globular masses unlike 

 any anatomical element ; others, especially those prepared at too low 

 a temperature, or with imperfect saturation, show masses of hexagonal 

 crystals like those of cystin. To sum up, I believe that there exists 

 in the cornea : — I., the fibrillary ground-substance, which is pierced 

 by straight canals and honeycombed with cavities; II., flat cells, 

 which everywhere cover the fibrillary bundles of the former and line 

 the entire system of the latter ; III., the cornea-corpuscles of Toynbee 

 and Virchow ; and IV., the nerve-structures of the tissue. The 

 cornea-corpuscles and the nerves lie free in the canals and cavities, 

 and between them and the epithelium there is a fluid-filled space 

 which permits the passage of lymph-corpuscles. It is therefore proper 

 to regard the canals, cavities, and interfibrillary spaces as forming a 

 continuous and integral part of the lymphatic system, the latter 

 having to the former the same relation that blood-capillaries have to 

 the veins. The junction of the flat cells of the fibrillary substance 

 with the epithelium of the surface justifies the inference that the 

 intercellular spaces in the anterior epithelium of the cornea commu- 

 nicate with the lymph-sjjaces in the ground-substance, and that the 

 position of nerve-fibrillfe between the epithelium is a continuation of 

 the similar relation that has been demonstrated in the substance of the 

 structure." 



