A New Disease of Cattle. 
239 
The same acid-fast bacteria are also present in the 
mesenteric glands in Johne’s Disease, but usually in smaller 
numbers than in the diseased intestinal mucous membrane. 
The facts already mentioned indicate that the bacillus of 
Johne’s Disease is an organism distinct from the bacillus which 
is the cause of tuberculosis in cattle, and the difference between 
them is further brought out when they are used to inoculate 
guinea-pigs. These animals invariably contract a fatal disease 
when they are inoculated with even minute numbers of bovine 
tubercle bacilli, but experiments which have been made in 
connection with the cases of Johne’s Disease observed in this 
country corroborate the observations previously made on the 
Continent, and prove that the disease is not transmissible by 
inoculation to the guinea-pig. 
Attempts were made to cultivate the bacilli from these cases 
of Johne’s Disease on artificial media, but hitherto without 
success. This negative result is in agreement with the expe- 
rience of those who have experimented in the same direction 
on the Continent. 
Probable habit of the bacillus of Johne's Disease . — A point 
of great practical importance in connection with every bacterial 
disease is to know whether it is a purely contagious one or 
whether it is sometimes or always sporadic. Whether a disease 
belongs to the first or the second of these categories depends 
entirely upon whether the bacteria are incapable of multiplying 
except in the bodies of infected animals or are able to main- 
tain their existence by multiplying in the outer world. In 
the latter case, the disease may obviously arise independently 
of contagion or infection, and it is equally obvious that in the 
former case no animal can ever, in natural circumstances, 
become infected except through the agency of bacteria which 
have come from a previously diseased animal. Applying these 
considerations to Johne’s Disease, one may ask whether the 
bacilli which are the cause of it are capable of multiplying 
outside the bodies of diseased animals — in the soil, in animal 
excrement, in water, on forage plants, or in decaying vegetable 
matter, for example. In view of the difficulty, amounting 
hitherto to an impossibility, of cultivating the bacillus artifici- 
ally, even under the most favourable conditions, this question 
must in all probability receive a negative answer. In other 
words, Johne’s Disease must be regarded as a purely contagious 
one, the vehicle of infection being the excrement of affected 
animals. As previously stated, in advanced cases of the disease 
the bacilli are present in enormous numbers in the lining 
membrane of the intestine, and some of them are constantly 
escaping into the bowel, to be passed outwards with the faeces. 
There is consequently no difficulty in understanding how the 
