Fig. 431, taken from another specimen of the same animal, shows the characteristic crescentic curve of the caecum and the corresponding course of the longitudinal muscular band. The apex of the pouch in this preparation is more rounded and blunt. The same blunt termination of the caecum of this type, with a corresponding sharper demarcation of the appendix, is seen in the gorilla (Fig. 457) recalling the conditions found in certain instances in the human subject (Fig. 522). 2. In by far the larger proportion of cases (ninety per cent. in Treves' series) the adult caecum obtains its characteristic form by an unequal development of the walls of the intestine. The right segment between the ventral and dorso-lateral muscular bands dilates, forming a sacculation which projects caudad and constitutes the secondary caput coli, while the segment between the lower border of the ileum and the original apex, marked by the origin of the appendix, remains stationary or is further reduced. This unequal development produces a relative displacement of the root of the appendix upward and to the left toward the ileo-colic junction. In some cases the primitive crescentic curve of the caecum, as indicated by the direction of the ventral longitudinal muscular band, is still perceptible. The right wall of the foetal caecum, forming the most pendent portion of the pouch, dilates uniformly and thus constitutes the adult caput coli. The left wall appears as a small sacculation separating the root of the appendix from the ileo-colic junction (schema, Fig. 509, _II, c_). This type of the adult caecum is illustrated by the preparations shown in Figs. 526-528. In other cases part of the right wall of the caecum between the ventral and dorso-lateral colic taenia, dilates abruptly forming a very prominent rounded sacculation which carries the lowest part of the pouch caudad in a sharper curve than in the preceding form as indicated by its deviation from the direction of the longitudinal muscular band (schema, Fig. 509, _II, d_). [Illustration: FIG. 526.--Human adult (Smith's Sound Eskimo). Ileo-colic junction and caecum; dorsal view. (Columbia University Museum, No. 61/1461.)] [Illustration: FIG. 527.--Human adult. Ileo-colic junction and caecum; ventral view. (Columbia University, Study Collection.)] [Illustration: FIG. 528.--Human adult. Ileo-colic junction and caecum; ventral view. (Columbia University, Study Collection.)] Figs. 529-531 afford examples of this type, while Fig. 532, taken from an infantile preparation, shows that the same may begin to develop at a very early age. [Illustration: FIG. 529.--Human juvenile. Ileo-colic junction and caecum; dorsal view. (Columbia University, Study Collection.)] [Illustration: FIG. 530.--Human adult. Ileo-colic junction and caecum; dorsal view. (Columbia University Museum, No. 115.)] [Illustration: FIG. 531.--Human adult. Ileo-colic junction and caecum; dorsal view. (Columbia University, Study Collection.)]