Fig. 123, taken from a foetus at term, shows the result of failure to completely rotate in the region of the caecum and ileo-colic junction. The rest of the large intestine has rotated as usual and assumed the normal position. The terminal ileum, however, passes behind the caecum and enters the large intestine on its right side; the caecum is turned upwards and to the right and the appendix lies ventrad of the beginning of the ascending colon. In order to produce the normal arrangement, shown in Fig. 124, taken from another foetus at term, it would be necessary to turn the caecum and ileo-colic junction in Fig. 123 through half a circle. The caecum would then turn upwards and to the left, the ileum entering the large intestine from left to right, and the appendix would be placed behind the caecum and ileo-colic junction. Figs. 125 and 126 show the normal and abnormal arrangement presented by these two preparations diagrammatically. The instances in which in the adult the ileo-colic entrance is placed on the right side of the large intestine and in which the appendix is situated laterad of the ascending colon unquestionably find their explanation in the failure of the intestine to completely rotate at the ileo-colic junction. [Illustration: FIG. 124.--Human foetus at term; abdominal viscera, hardened _in situ_; normal position of completely rotated caecum and appendix. (Columbia University Museum, No. 1814.)] [Illustration: FIG. 125.--Just before final rotation of caecum and terminal ileum. Concavity of caecum directed cephalad and to right. Terminal ileum enters colon from right to left.] [Illustration: FIG. 126.--Rotation completed. Concavity of caecum turns caudad and to left. Terminal ileum enters colon from left to right.] [Illustration: FIGS. 125, 126.--Schematic representation of final stages in rotation of caecum and large intestine.] The resulting conditions are shown in Figs. 127 and 128, taken from adult human subjects in which the final stage of rotation of the large intestine has not taken place. [Illustration: FIG. 127.--Adult human subject with non-rotated caecum. The terminal ileum turns caudad from right to left to enter right side of colon.] [Illustration: FIG. 128.--Adult human subject with non-rotated caecum, the ileum entering large intestine from the right and behind, and the appendix placed to the right of the ascending colon. (From a fresh dissection.)] In Fig. 127 the terminal ileum is sharply bent on itself and adherent to the prerenal parietal peritoneum. It passes from right to left and downwards to enter the right posterior circumference of the large intestine. The caecum is turned cephalad and the appendix is in contact with the right lobe of the liver. The caecum passes with a sharp bend into the obliquely directed ascending colon.