HIS, ON THE CORNEA. 51 
these acids may be added to a section after it is covered, and 
will be found, after a few hours, to have done its work with- 
out disturbing the relations of the unattacked parts. 
Pursuing these various modes of investigation, and using 
the one as a check upon the other, Dr. His has arrived at 
the following results. 
The cornea and the sclerotic are, as has for some time been 
maintained by the most trustworthy observers, perfectly con- 
tinuous ; the tissue of the latter gradually passing into that 
of the former organ, but assuming a more regular arrange- 
ment, and appearing lamellate instead of areolar. The ele- 
ments of the cornea appear to be arranged circularly at the 
margin of both its most superficial and its deepest layers, 
crossing one another towards the centre. In the interme- 
diate substance, on the other hand, or middle layer of the 
cornea, the disposition is radial. 
Anteriorly the cornea appears to be bounded by a. struc- 
tureless layer—the “anterior elastic lamine” of Bowman ; 
posteriorly is a similar but thicker stratum—the well-known 
membrane of Demours or Descemet. The latter is easily de- 
tached, but the former cannot by any procedure be cleanly 
separated from the subjacent tissue. In fact, it would appear 
that the intercellular substance of the cornea passes at 
intervals completely into the anterior elastic lamina, thus 
constituting the “fibrous cordage” of Bowman. Dr. His 
says— 
“ Approximating to Reichert’s view, I am inclined to think that the anterior 
lamina and membrane of Descemet both originate in a more abundant 
deposit of intercellular substance, which, projecting beyond the level of the 
strata of cells, subsequently becomes differentiated from the other inter- 
cellular substance. The membrane of Descemet becomes more differentiated 
than the anterior lamina; the latter constituting, as it were, a sort of 
transitional formation between the intercellular substance and Descemet’s 
membrane. As for the difference in point of separability between the 
membrana anterior and membrana Descemetii, it must be remembered, 
Ist, that the distinctness of the latter depends on circumstances, and that 
it can hardly be separated in a fresh eye without carrying away with it 
some portions of substantia propria; 2d, that the much more parallel 
lamination or cleavability of the deeper layers of the cornea, as compared 
with the superficial ones, greatly favours the more easy separation of the 
membrane of Descemet. ‘The anterior lamina becomes lost at the edge of 
the cornea, passing into a simple, sharply defined, dark line, which bounds the 
conjunctiva anteriorly. The anterior Jamina is not so universally present as 
the membrane of Descemet ; while I found it very beautifully developed in 
man, the ox, the sheep, the pig, the rabbit, and the Guinea pig, as well as 
in pigeons and rooks, I could not discover it in the horse, the goat, the 
dog, or cat. In the latter animals the epithelium lies directly upon the 
cellular substantia ropria, and the surface, when the epithelium is removed, 
appears uneven all drawn in, at those places where the ‘fibrous cordage’ 
