| Bacillary | Amœbic |
| An acute diffuse inflammation of the mucous membrane of the large intestine, leading to necrosis and destruction of glandular tissue. | A local lesion of the large bowel, with characteristic ulceration due to penetration of mucosa and submucosa by amœbæ. |
| No diffuse necrosis except in cases where secondary bacterial infection has taken place. | |
| Ileum often affected. | Ileum rarely affected. |
| Perforation of intestine and intestinal adhesions rare. | Perforation of intestine and intestinal adhesions common. |
| In some cases hæmorrhage and destruction of nutrient vessels and infiltration of submucosa to such a degree as to render recovery of function impossible. | Infiltration of submucosa not marked. Local ulceration often extends down to serous coat. |
| Other organs not implicated. | Liver often implicated. |
| B. dysenteriæ can be isolated from necrosed mucous membrane and from the stools. | Amœbæ demonstrable in local lesions and in the stools. |
As already indicated, mixed infections of both forms may occur.
Balantidium Dysentery
The occasional occurrence of Balantidium coli in the fæces, particularly in association with dysenteric diarrhœa, has been recognized for the last fifty years. It is only lately, and more particularly since Strong and Musgrave called attention to the subject, that B. coli has come to be regarded as the germ cause of a particular type of colitis resembling in many respects amœbic dysentery. The parasite has been studied zoologically, more especially in temperate climates, but it seems probable that extended observation will show that the balantidium is equally if not more prevalent in warm climates.
Balantidium coli is an oval-shaped ciliated infusorian measuring 0·07 to 0·1 mm. by 0·05 to 0·07 mm. Its anatomical characters may be gathered from Fig. 82. It reproduces by division, budding, and conjugation. Occasionally, losing its cilia, it may become encysted.
