POST-MORTEM EXAMINATION 47 



that, beyond the intestinal mucosa and the colic and 

 mesenteric lymphatic glands, no other lesions con- 

 taining bacilli in a naturally contracted case have been 

 recorded. As a rule the ileo-caecal valve and the last 

 part of the ileum ma}^ be expected to show the most 

 marked lesions. 



Even when experimental animals are fed with in- 

 fective material, or pure cultures of Johne's bacillus, 

 or are inoculated intravenously, intraperitoneally, or 

 subcutaneously, the disease is developed in the small 

 intestine ; and except in the case of subcutaneous 

 injections, which in some cases have caused a small 

 localized abscess, no other lesions containing bacilli 

 are demonstrable post mortem. 



Before cutting into the intestine one can often 

 perceive the thickening of the small bowel by taking 

 it between the finger and thumb and comparing it in 

 various places. In a bad case some parts are appre- 

 ciably thicker than others, but there is never any 

 evidence of the disease on the peritoneal membranes. 

 A variable length of the intestinal tract seems to be 

 affected. Measured from the ileo-caecal valve, the 

 small intestine for about 30 feet often shows evidence 

 of disease ; sometimes the length infected is as much 

 as 70 feet. The initial part of the duodenum in cattle 

 seems never to be affected ; but the disease may 

 extend as high up as Vater's ampulla, and in one of 

 our naturally infected cases this was extensively 

 involved. 



A badly -affected piece of bowel shows marked 

 thickening, and the mucous membrane is thrown into 

 characteristic corrugations. These corrugations are 

 often broken up into small islands which give a warty 

 appearance to the surface of the gut. In a piece of 

 normal small intestine from which the fat, etc., in the 



