[Illustration: FIG. 150.--Caudal portion of human embryo of 5 mm., with the end- and caudal gut at the highest stage of its development. x 25. (Reconstruction after His.)] The early position of the colon produced by the large size of the foetal liver, and before the descent of the caecum has occurred, is shown in Fig. 124. In Fig. 123, where the liver has regained its normal proportions with reference to the abdominal cavity and viscera, and the caecum has descended into the right iliac fossa, the hepatic flexure is well marked and the first segment of the colon has acquired the vertical position on the right side, the single obliquely transverse segment of Fig. 124, having become divided into an ascending and a transverse colon. [Fig. 124. Early stage. Liver relatively large. Proximal portion of the colon extends obliquely between the right lumbar region and the spleen. The caecum has not yet descended. Fig. 123. Later stage. The caecum occupies the right iliac fossa. Relative reduction in the size of the liver allows the colic segment to be divided by the hepatic flexure into an ascending colon and a transverse colon.] At times the transverse colon, whose normal average length in the adult is 20", greatly exceeds this measurement and forms an arch which hangs down or makes a well-marked V-shaped bend with the apex directed toward the pubes. This is the normal arrangement of this portion of the large intestine in many of the lower primates. Fig. 151 shows the abdominal viscera of _Macacus rhesus_, hardened _in situ_, seen from the front and the right side, with the omentum turned up over the stomach. The transverse colon forms an extensive V-shaped bend, whose apex reaches to the pubes, from which point the large intestine turns again cephalad and dorsad to form the splenic flexure and then descends to the pelvis. [Illustration: FIG. 151.--Abdominal viscera of _Macacus rhesus_, rhesus monkey, hardened in situ. (Columbia University Museum, No. 1817.)] The average length of the ascending colon in the adult, measured from the tip of the caecum to the hepatic flexure, was found by Treves in his series of 100 bodies to be 8", while the descending colon, from the splenic flexure to the beginning of the sigmoid loop, measured 81/2". The descending colon may at times be much longer, up to 15", and become convoluted.