48 JOHNE^S DISEASE 



mesentery has been cleared away, and which has been 

 cut open longitudinally, a number of small folds are 

 seen ; but if the bowel is stretched as widely as pos- 

 sible these folds disappear. In a case of Johne's 

 disease it is not possible to make these corrugations 

 assume the level of the normal intestine. The same 

 remarks apply to the caecum, which is very frequently 

 affected, though in this part of the bowel the lesions 

 are inclined to be more patchy. 



Occasionally the thickening is hmited to small 

 portions of the bowel; a few feet may be markedly 

 affected, then an interval of sound or apparently sound 

 intestine may intervene, and then another portion of 

 diseased intestine may be found. The small intestine 

 may escape entirely, and lesions be present only in 

 parts of the large bowel. Apparently the naked-eye 

 evidence of the disease is no guide to the number of 

 bacilli that may be found beneath the surface. This 

 has been well shown in a case examined by M'Fadyean, 

 Sheather, and Edwards, in which, post mortem, the 

 small intestine showed no macroscopic evidence of 

 disease ; yet smears taken from the mucosa of the 

 last 90 feet were found to be quite rich in acid-fast 

 bacilli. 



If a portion of intestine is badly affected acid-fast 

 bacilli are, as a rule, to be found in the neighbouring 

 lymphatic glands; but this is subject to considerable 

 variation, as in some cases the bacilli are unexpectedly 

 numerous, and in others none can be found. The 

 colour of the corrugated mucous membrane in a well- 

 marked case is rather characteristic, being of a pinkish- 

 yellow tint, with occasional patches of congestion ; but 

 there is never any erosion of the surface of the mucosa, 

 or any tendency to ulceration, unless the animal has 

 been killed shortly after a dose of diagnostic vaccine 



