VETERINARY OPHTHALMOLOGY. 
679 
or when there is an obstruction to the capillary circulation. 
It occurs in what is called mucous infiltration, colloid infil¬ 
tration, amyloid infiltration. 
Ulceration of the cornea is the consequence of colloid necro¬ 
biosis of the membrane. It is caused by general debility; 
occurs specially in old dogs weakened by misery, diseases, 
old age; in young dogs as a result of long and protracted dis¬ 
temper or any other cause of general debility. 
At the outset there is no sign whatever of irritation ; the 
eye keeps open, the cornea is transparent except at a small 
spot in the centre generally, or near the centre, but not always^ 
as is thought by the above named writer, and as my case will 
prove. The non-transparent part of the membrane appears 
■ as a small speck of a milky color and slightly bulging out. 
Later on the affected part softens, colloid degeneration 
takes place, it falls off and leaves'in its place a small cavity, 
nearly circular, surrounded by a grayish, white zone. Vision 
is not affected yet. 
The cavity grows larger, more or less rapidly, according 
to the conditions of existence, until half or two-thirds of the- 
thickness of the cornea has been invaded. At this period the 
eye may not be painful and the eyesight not much impaired. 
Then, should the causes continue to exist, and the ulcera¬ 
tion not attended to properly, it keeps on growing larger and 
deeper until the membrane is perforated through ; the mem¬ 
brane of Descemet shows itself into the opening in the shape 
of a small, round hernia. From this period inflammation sets 
in, affecting first the membrane of Descemet and the cornea 
afterward. In the mildest cases this inflammatory reaction 
may bring on cicatrization of the ulcer. In the worst cases the 
membrane of Descemet, being exposed, breaks; the aqueous 
humor flows out, and the inflammatory process invades the 
serous cavity and terminates in total loss of the eye. In other 
cases again, the ulceration is so large that the crsytalline lens, 
not being kept in place, falls out. 
Here is a case of this kind : The patient is a very old dog— 
sixteen years old, deaf and almost blind, suffering for a long 
time from general debility, brought on by chronic gastro-en- 
