A corresponding arrangement is noted in the preparation of the caecum of _Cercopithecus campbellii_ (Fig. 433). The large intermediate fold is joined by the ventral vascular fold, thus defining the lower boundary of ventral ileo-caecal fossa. (_C_) _Union of both vascular folds with the intermediate non-vascular fold._ I have encountered one instance of this arrangement in an infant, whose caecum and ileo-colic junction is shown in Fig. 580. Both the ventral and dorsal arteries in this case were equally developed, and shared equally in the supply of caecum and appendix. Both vascular folds fused with the intermediate fold, thus producing two typical ileo-caecal fossae, one ventral, the other dorsal. [Illustration: FIG. 580.--Human infant. Ileo-colic junction and caecum; fusion of ventral and dorsal vascular folds, with intermediate fold. (Columbia University Museum, No. 1663.)] (_D_) _Abnormal positions of the appendix due to variations in the arrangement and tension of the intermediate fold._ Fig. 510 shows a foetal caecum in the ventral view. The ventral vascular fold (3) is well developed. The non-vascular fold is short, arising from the ventral surface of the ileum, instead of from the free border of the intestine opposite to the mesenteric attachment. It fuses with the ventral vascular fold a short distance below the ileo-colic junction, thus limiting a small ventral ileo-caecal fossa. The dorsal caecal artery in this specimen was large, but the fold carrying it extremely narrow. The preparation illustrates the type resulting from the reduction in size and extent of the non-vascular and mesenteric folds. The intermediate fold is reduced to a short and narrow band. Compared with the usual infantile type the caecum lacks the characteristic turn upwards and to the left, possibly in consequence of the slight traction caused by the rudimentary intermediate fold. The pouch occupies a nearly vertical pendent position, which the appendix, arising from the lowest point of the caecal funnel, shares. The appendix is not drawn into the retro-ileal position by the dorsal vascular fold, which is much reduced. In Fig. 511, representing the caecum and appendix of a foetus at term, the effect of the tense non-vascular intermediate fold (2) is seen in the sharp turn to the left which it imparts to the nearly transversely directed funnel-shaped caecum. The appendix (1) is coiled spirally for 13/4 turns behind the ileo-colic junction, with the tip directed upward behind the mesentery of the terminal ileum. The non-vascular intermediate fold (2) extends to the rest of the appendix. It appears short in its caecal attachment, on account of the turn of the caecum backwards and to the left and the close connection between the adjacent margins of the ileum and caecum. [Illustration: FIG. 581.--Human foetus at term. Ileo-colic junction and caecum. (Columbia University, Study Collection.) 1. Appendix, terminal portion turned ventrad of ileo-colic junction.