194 JOHNE’S DISEASE 
intestine is most often involved. The lesion is in the mucous and 
submucous tissue. In some cases the acid fast bacteria invade the 
submucosa in which case the wall of the intestine becomes thickened. 
According to Sheather a variable amount of new cellular tissue com- 
posed of cells of the epithelioid type, and containing an occasional 
giant cell, is. developed beneath the epithelium and often also in the 
submucous layer. In proportion to its thickening the mucosa 
shows more or less coarse wrinkling. Ulceration is not observed. 
There is little congestion on the tops of the folds of the mucous tissue. 
The mesenteric lymphatic glands may be enlarged. They may 
contain collections of epithelioid and giant cells. Meyer found more 
or less edema of the abomasum in about 40 per cent. of his cases. 
The atrophy of the spleen with a brownish dry appearance of the 
pulp was always present and he found clumps of pigment often in 
large amounts. This condition was first mentioned by Bang. When 
cut an appreciable amount of water-like liquid exudes from the surface. 
The absence of congestion has been noted. 
The most striking feature of the disease is the slight tissue changes 
even when the bacteria are exceedingly numerous. In sections made 
at right angles to the mucous surface of the intestine an irregularity 
in the size and outline of the villi can be observed. Some of the villi 
may be partially denuded of epithelium. In the glandular layer the 
interstitial tissue between the tubular glands may be increased in 
amount and the glands may show evidence of atrophy. In sections 
stained by the Ziehl-Neelsen method, with Pappenheim’s stain for 
contrast, M’Fadyean states that those parts in which the bacteria are 
numerous have an appearance very similar to that of a genuine tuber- 
culosis lesion just before the onset of necrosis and caseation, that is, 
they appear to be mainly made up of the so-called epithelioid cells, 
with occasionally a well formed giant cell. Sometimes the outlines of 
these epithelioid cells are distinct, but, as a rule, wherever the bacilli 
are numerous there appears to have been a partial fusion of the cell 
bodies, and the appearance is that of a sort of matrix substance with 
imbedded nuclei. The majority of these nuclei are shrivelled or dis- 
torted in appearance, and they stain lightly as compared with any of 
the nuclei in the surrounding normal tissue. According to M’Fad- 
yean, the important points to notice are that the diseased tissue is 
never sharply circumscribed and that there is no actual necrosis, 
although the appearance of the new tissue may be interpreted as 
indicating that the cells are on the point of losing their vitality. 
