260 The Mi aigenieitt and Diseases ws the Dog. 
gnomy has long fees recognised as an_ essential 
part of the diagnosis, and that this characteristic in- 
dication is largely due to the dull heavy eyes, 
which are so commonly partially covered by the membrana 
nictitans in rabies. Besides, the malady has a tendency to 
be accompanied by catarrh of the conjunctive, indicated by 
a collection of mucus in the inner canthus of the eye. Be- 
yond this, there sometimes suddenly appear circumscribed 
opacities of the cornea, with breaking up of its texture in 
the centre of these, and so leading to the formation of ulcers. 
This ulceration progresses so rapidly, that in some cases 
the substance of the cornea is perforated within two days. 
These corneal ulcerations are not, however, very common: 
Siedamgrotzky had only observed them in six cases, in 
which two or three ulcers appeared in both eyes. They 
are not an accompaniment of only one form of rabies, but 
appear in both—dumb as well as furious. On a post-mortem 
examination, it is found that the ulcer has penetrated the 
cornea, in a conical manner, and that nothing but a thin 
layer of fibrin, or a blood coagulum in the anterior chamber, 
has prevented the escape of the entire contents of the organ. 
Examined microscopically, the corneal ulcer offers no 
essential difference from that witnessed in distemper: 
moderate cell-heaping in the vicinity of the ulcer, fatty 
degeneration of the corneal elements, and opening out 
of the interstitial substance; but nothing otherwise cha- 
racteristic. j 
Siedamgrotzky at first believed that the alteration was 
produced by mechanical causes, but from close observation - 
he is satisfied that it may appear in the quietest animals 
whose eyes have not been exposed to external injury. It 
is therefore not unlikely that an interruption in the nutrition 
is the cause; though not a general alteration in the nutritive 
function, but perhaps rather due originally to an alteration 
in the trophic nerves of the eye. 
This explanation, of course, cannot be experimentally 
