20 
PROGRESS OF MICROSCOPICAL SCIENCE. 
In the fresh frog's cornea examined entire in serum, the structure, 
looked at through the anterior epithelium, can be seen to be broken 
up by clefts, the borders of which have a double contour. These 
clefts extend from the epithelium to a varying depth into the fibrillary 
tissue. They are arranged sometimes concentrically, and sometimes 
in waving lines, which give off branches which are narrower as they 
approach the centre of the cornea. The double-contoured borders are 
not parallel to the median plane of the cornea, and can be traced only 
by changing the focus. 
From the existence of these clefts the author infers a division of 
the cornea substance into compartments equivalent to the secondary 
and tertiary bundles of tendon. 
In inflammation the clefts are much widened, and their finer rami- 
fications become visible. In preparations of inflamed cornea different 
tracts of cornea substance bounded by the clefts are coloured of diffe- 
rent shades by chloride of gold, the difference affecting the fibrillary 
tissue, and more markedly the spindle-cells. 
The serous contents of the interspaces of the inflamed cornea differ 
in character from those of the healthy cornea, inasmuch as the former 
show, more abundantly, the dark granular substance which results 
from the reduction of the chloride of gold. 
In a very early stage of inflammation (after a few hours) the dis- 
tension of the narrow spaces between the primary bundles and of the 
wider and more yielding spaces between the lamellss, corresponding to 
the larger bundles, favours the action of chloride of gold ; and pre- 
parations can thus be obtained by this reagent which show that the 
two kinds of flat cells which cover the respective surfaces are arranged 
after the manner of an epithelium. The cells thus seen can be iden- 
tified by their size, contour, and arrangement, as those which are 
isolable from the healthy cornea by warm saturated solution of caustic 
potash, and which can be seen in preparations sealed up in aqueous 
humour. 
A similar distension occasionally permits the demonstration of the 
layers covering the secondary bundles of tendon. 
That the successful gold reaction in such cases is probably due 
solely to the distension of the interspaces, is inferred from the fact 
that in the tendo Achillis of frogs which have died from disease, and 
have been some hours in water after death, the author has obtained 
gold preparations showing not only the cells of the secondary bundles 
(Ranvier's cells), but also small groups of the long narrow cells which 
cover the primary bundles. 
In the cauterized frog's cornea, examined in blood-serum after 
twelve hours' inflammation, portions of the primary bundles are found 
lying loose on the surface. These detached portions have a nearly 
constant length, a uniform breadth, sharply-defined even borders, are 
sometimes puckered transversely, occasionally show a faint appearance 
of longitudinal fibrillation, and are sometimes cut transversely, at one 
or more points, by straight hyaline lines. They resemble accurately 
the primary bundles of the neurilemma of the sciatic nerve and the 
rods of the retina of the healthy frog. 
