238 Annual Report for 190fi of Royal Veterinary College. 
In the other cases examined no trace of tuberculosis was 
found anywhere. In three of the cases examined the fourth 
or true digestive stomach appeared to be perfectly normal. In 
the fourth animal the mucous membrane of this stomach was 
in a markedly oedematous or dropsical condition, and there 
were numerous very shallow erosions on it. 
Microscopic examination is necessary in order to ascertain 
what is the nature of the alteration which produces the 
thickening of the intestinal mucous membrane, and such 
examination at the same time reveals the cause of the disease. 
As Johne and Frothingham discovered, the diseased mucous 
membrane contains immense numbers of a small bacillus which 
is not unlike the bacillus of tuberculosis in shape and size, and 
which resembles that organism still more closely in what may 
be called staining reactions. The tubercle bacillus is the most 
important member of the group of what are called acid-fast 
bacteria, the distinguishing character of which is that when 
once they have been stained with any one of the dyes in 
common use in bacteriology they cannot readily be decolourised 
even by the use of strong acid solutions. The bacillus of 
Johne’s Disease is one of these acid-fast organisms, and by 
taking advantage of this fact it is very easy to demonstrate the 
presence of the bacteria in sections or even in scrapings from 
the diseased mucous membrane. In most of the cases that 
have been examined the number of these bacteria present in 
the thickened mucous membrane was colossal, and a marked 
feature of them is their tendency to be aggregated into 
comparatively large groups. As previously stated, the bacteria 
in question are not unlike tubercle bacilli in shape and size, 
but on an average they appear to be somewhat smaller. 
The microscopic alterations in the diseased mucous 
membrane comprise a partial destruction of its surface 
epithelium, and of the epithelium of the villi in the case of 
the small bowel, and also an addition of a certain amount 
of new cellular tissue between the tubular glands and in the 
substance of the villi. This cellular infiltration frequently 
extends to the sub-mucous coat, immediately under the deep 
ends of the tubular glands. It is in this new cellular 
material that the bacilli are found imbedded. Contrary to 
what is the case in tuberculous lesions, the cellular infiltration 
or multiplication is quite diffuse, and not in the form of 
nodules or tubercles. A further distinction between the two 
processes is that in Johne’s Disease there appears to be no 
tendency to the peculiar tissue degeneration called caseation, 
or to calcification. On the other hand, the two processes 
resemble each other in that giant cells are often present in 
their respective lesions. 
