PATHOLOGICAL HISTOLOGY 59 



The extent of the alteration in the bowel seems to 

 bear little, if any, relation to the intensity of the clinical 

 symptoms that are shown by the animal. B. Bang 

 states that in cases in which the clinical symptoms are 

 very marked there is often only a slight thickening of 

 the mucous membrane, and sections show but a 

 trifling infiltration with epithelioid cells. The extent 

 of the pathological changes found in the mesenteric 

 and colic lymphatic glands is usually proportional to 

 the extent of the lesions in the gut; in some cases, 

 however, this is not so, and the glands may be but 

 little affected in a fairly advanced case. The extent of 

 the glandular lesions varies considerably in different 

 cases, and in an advanced stage of the disease the 

 condition of the glands may be oedematous, or may 

 show a considerable destruction of the normal lym- 

 phatic tissue. 



The usual change found microscopically is an 

 oedematous condition of the organ, the intracellular 

 connective tissue of which is prominent ; while the 

 lymphatic cells, instead of being closely packed, as in 

 a normal gland, are somewhat loosely arranged. This 

 is especially marked in the centre of the gland. In 

 many cases no other lesions can be found, and the 

 presence of bacilli, even after a careful search, cannot 

 be demonstrated. In these simple cases, however, it 

 is usual for a small number of bacilli to be present. 

 Sometimes the glands are markedly changed, and 

 numerous epithelioid and giant cells, accompanied by 

 masses of acid-fast bacilli, are found. 



It is well to remember that, if an animal dies or is 

 killed shortly after the inoculation of a diagnostic 

 vaccine, microscopical examination of the organs shows 

 an intense congestion of the tissues, especially in the 

 lymphatic glands. This may give rise to an entirely 



