232 johne's disease 



The mesenteric lymphatic glands ma}' be slightly en- 

 larged. 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 num- 

 erous. In sections made at right angles to the mucous sur- 

 face of the intestine an irregularity in the size and outline of 

 the villi can be observed. Some of the villi mav be partially 

 denuded of epithelium. In the glandular layer the inter- 

 stitial tissue between the tubular glands may be increased in 

 amount and the glands may show evidence of atrophy. In 

 sections stained bj' the Ziehl-Neelsen method, with Pappen- 

 heim's stain for contrast, M'Fadyean states that those parts 

 in which the bacilli are numerous have an appearance very 

 similar to that of a genuine tuberculous lesion just before the 

 onset of necrosis and caseation, that is, the\' appear to be 

 mainly made up of the so-called epithelioid cells, with occa- 

 sionall}' 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 vesicular but shrivelled or distorted in appearance, 

 and they stain lightly as compared with anj^ of the nuclei in 

 the surrounding normal tissue. According to M'Fadyean, 

 the important points to notice are that the diseased tissue is 

 never sharply delimited 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. Within the parts which contain large numbers of 

 bacilli there are also sometimes recognizable small round com- 

 pact nuclei, apparently belonging to cells of the lymphocyte 

 type, and at their margins there are numerous cells whose 

 bodies stain red with Pappenheim's stain. 



The bacilli do not appear to be specially intra-cellular ; 

 many of them seem to be h'ing free, and others appear to be 



