Foot-rot in Sheep. 
745 
2. Indicates the presence of a hollow cavity containing dirt. 
'6. The minute fissure, apparently superficial, existing as a dark line upon 
the wall of the foot. 
The precise structural alterations which result from foot-rot 
appear to be the following : — 
a. Mechanical derangement of the structure of the hoof and the intro- 
duction of gritty particles into the canals or into accidental fissures. 
b. Softening and disintegration of the horny structure by the moisture of 
the soil and the exuded fluids from the internal membrane. 
c. Irritation of the internal membrane, causing excessive secretion of 
epithelial cells with serous exudation, associated with increased vascularity 
and sensibility. 
Subsequently, in 18G8, Professor Brown communicated to 
the same Journal another paper, " Observations on the Diseases 
of the Foot of the Sheep generally comprehended in the term 
Foot-rot ; with a Report of Experiments which were carried out 
for the purpose of deciding the disputed question of the con- 
tagious or infectious nature of these diseases." On this occasion 
it was remarked : — 
"Many authorities adopt the conclusion that foot-rot depends upon local 
conditions, and is altogether unconnected with infection. Others assert the 
disease to be so contagious that a single animal affected with foot-rot, if 
introduced among a healthy flock, is capable of communicating the disease, 
and that not only to the sheep with which he comes in contact, but in a 
manner also to the land, so that the previously healthy soil acquires a new 
character, and becomes foot-rotting land." 
The difficulty attending the inquiry was illustrated in the 
following extract from the first paper : — 
" Most of the information conveyed to us comes from men who were not 
acquainted with the characteristic elements of the disease, and who seem to 
have recorded effects irrespective of their possible causes, giving, in place of 
logical deductions, the mere impressions which the facts made on their own 
minds at the time of their occurrence. The only direct evidence bearing 
upon the question refers to inoculation, and the conveyance of the disease 
by an infected animal to a perfectly healthy locality. On both these points 
the results recorded by different observers are opposed. The facts advanced 
on one side prove that the disease will spread from a diseased sheep to 
healthy animals in a previously healthy situation ; and, further, that direct 
contact of a healthy foot with the matter from a diseased one will induce 
the disease. The facts on the other side prove that a diseased sheep may 
with impunity be allowed to mingle with healthy ones on a dry soil, and 
that contact with the matter of ' foot-rot ' is not injurious unless the healthy 
foot has been previously denuded of a portion of its horny covering." 
After recording various cases of conflicting evidence, the 
author proceeded : — 
" Nothing can be more graphic than the descriptions which have been 
uoted, and, if read in the light of recent experience, they furnish a clue to 
