The Caecum is that portion of large intestine which lies below the entrance of the ileum. It is normally situated in the right iliac fossa, its most dependent part midway between the anterior iliac spine and symphysis pubis, and measures 2 inches vertically, and 3 inches in diameter. When empty it is generally covered by other loops of bowel, but when full lies in contact with the abdominal wall. In herbivora the caecum is very large, and developmentally in man the appendix forms the tapering extremity of the caecum, this ' infantile type ' sometimes persisting. The caecum, like the colon, is possessed of three longitudinal bands, one of which is situated anteriorly, and the others postero-externally and internally respectively. The caecum falls from these bands in saccular folds, and, in addition, owing to shortness of the internal band, it is curved, with the concavity to the left. In the adult type this curving becomes more marked, as does likewise the sacculation between the anterior and postero-external band9, until finally this saccule becomes the most dependent part, and the appendix appears tucked up and attached to the inner and posterior wall. As these bands are continued into the appendix, the anterior one is sometimes taken as a guide to the appendix. It should be remembered that develop-mentally the caecum first lies on the left side, and then crosses to the right, lying at first in front of the right kidney, and then descending toward the pelvis. This fact may account for the caecum being found occasionally in left-sided inguinal and umbilical herniae. Further, as the caecum is generally entirely invested with peritoneum, it is comparatively mobile. Sometimes it retains its foetal mesentery, and from this cause, also, may, along with the appendix, form the contents of a hernia on the right, or even on the left, side, or become affected by volvulus. Foreign bodies may sometimes lodge, and concretions may form, in the caecum, and cause ulceration. Where there is obstruction in the large intestine, the caecum tends to become distended with faecal matter, sometimes becoming very large, and occupying a large portion of the abdominal cavity. An examination, therefore, of the caecum may, in a case of doubt, assist in determining whether an obstruction exists above or below the ileo-ccscal valve. If the former, the caecum will be normal; if the latter, it will probably be distended ; and in such cases it is prone to stercoral ulceration, which may lead to perforation. Dysenteric and tubercular ulcers also occur in it.