JOHNE’S DISEASE 193 
the tissues appear to be almost powerless to restrain its multiplication 
and invasion. 
The period of incubation is not determined but it is known to be 
long, possibly a year or more. 
Symptoms. The first symptom to be observed is a loss of flesh, 
although the appetite remains normal. The hair becomes roughened 
Fig. 46. A PHOTOGRAPH OF A PORTION OF THE SMALL INTESTINE OF A COW DEAD OF 
JOHNE’S DISEASE. NATURAL SIZB. 
and the animal presents an unthrifty appearance. Diarrhea sets in 
early and usually it is profuse and persistent from the time it begins, 
although it may sometimes be checked temporarily by giving dry 
food and by the administration of astringents. Emaciation becomes 
a prominent symptom. 
Morbid anatomy. The lesions are primarily in the large and small 
intestines and associated lymph glands. The distal part of the small 
