Tuberculosis of the intestines is of very frequent occurrence. While it usually appears in phthisical patients, there are also cases of an undoubted primary intestinal tuberculosis. According to Frerichs, 1 a tuberculous affection of the ileum is found in eighty per cent of the cases of chronic pulmonary phthisis. Bayle in 1810 was the first to observe the occurrence and frequency of tuberculous ulcers of the intestine. The seat of these ulcers is principally in the ileum, especially in its lower portion. They may extend from this point downward over the colon to the rectum or upward over the entire ileum, jejunum, and even the duodenum.

1 E. Frerichs: "Beitrage zur Lehre von der Tuberculose, "Marburg. 1882.

The development of the ulcer takes place in the following way: In one of the solitary follicles a miliary tubercle forms by extensive accumulation of cells, the latter swell up; after a time a caseous degeneration appears in the centre and the swollen follicle bursts; thus a small pea-sized ulcer is formed. In the same way tuberculous processes may develop in the agminated follicles and also lead to the formation of ulcers. But whereas Peyer's patches are equally affected in their entirety in typhoid fever and intestinal catarrh, in tuberculosis the infiltrations are confined only to several follicles of the group, while others belonging to the same patch remain intact.

The ulcer enlarges either by spreading directly at the periphery or by the coalition of several defects. As a rule the extension of ulcers into the deeper layers proceeds in a line transversely to the intestinal lumen corresponding to the direction of the vessels supplying the bowels. Thus in the small intestine the ulcer spreads in a line parallel with the valvulae conniventes, and thus may form a circular defect over the entire lumen of the intestine, transversely to its longitudinal axis (the so-called tuberculous girdle ulcer). There exist, however, ulcers of an oblong or entirely irregular shape. With regard to the depth of the ulcer it usually penetrates to the muscularis and remains at a standstill there. Small tuberculous foci, however, are often met with within the latter, usually connected with the lacteals. Sometimes a destruction of the muscular layers is also present and the ulcer may advance down to the serosa and may even perforate into the peritoneal cavity.

The fully developed large tuberculous ulcer has an irregular shape, and mostly a bright red margin, being partly smooth, partly overlapping, sometimes undermined. Its base is pultaceous, consisting partly of decomposed tissue, partly of swollen remnants of the mucosa. Tuberculous infiltrations are noticeable here and there at the base as well as at the margin. The surroundings of the ulcer often show catarrhal changes. The serosa over it is usually in a state of chronic inflammation, being reddened, thickened, and surrounded with fibrinous exudations. Sometimes there are agglutinations with other intestinal coils, the omentum, or other immediately adjacent organs. The frequency of these peritonitic adhesions explains why perforations of tuberculous ulcers within the intestine are comparatively so rare.

Tuberculous ulcers very rarely show a tendency to heal, the process as a rule progressing steadily and leading to the formation of new nodules in the neighborhood of the margin. In very few instances, however, cicatrization of the ulcers takes place. The latter, when occurring in ulcers of girdle shape, may produce a stenosis of the intestinal lumen.

Tuberculous ulcers are very rarely primary, that is to say, developing in the intestines without a previous tuberculous affection existing in other organs. In most instances they are secondary and are met with in patients who are in a more or less advanced stage of pulmonary tuberculosis.

The ultimate cause of tuberculous processes in the intestine is Koch's tubercle bacillus. The latter may be carried into the intestinal canal with the sputum which phthisical patients swallow, or it may also, in rare instances, be ingested directly with the food. Thus, meat and milk of tuberculous cows may cause primary tuberculosis of the intestine. This condition is specially frequent in infants on account of their being fed with milk either from phthisical nurses or tuberculous cows.