The significance and mutual relations of the folds seen in the preparations just considered—which illustrate the typical adult human arrangement of the structures—will perhaps be best understood by comparison with an adult cæcum in which the infantile condition, as seen in [Fig. 563], has become further developed.
Fig. 567.—Human adult. Ileo-colic junction and cæcum; dorsal view. (Drawn from preparation in Columbia University, Study Collection.)
1. Dorsal vascular fold, carrying the distal appendicular branch of the dorsal cæcal artery in the mesentery of the appendix.
2. Proximal branch of the same vessel, turning downward to cæcum and root of appendix.
3. Intermediate non-vascular fold.
Fig. 567 shows the dorsal view of such a preparation. The cæcum is funnel-shaped with the apex, carrying the root of the appendix, turned upward and to the left, the sacculation to the right of the ventral muscular band being somewhat dilated. The appendix—7.2 cm. long—turns sharply upward and to the left, closely applied to the left cæcal sacculation, passes dorsad to the ileo-colic junction and lies in its terminal part under cover of the ileo-colic mesentery. The ventral branch of the ileo-colic artery descends over the ileo-colic junction, supplying the ventral wall of the cæcum. The intermediate non-vascular fold (3) is 3.9 cm. long and entirely free.
The dorsal vascular fold contains the large dorsal branch of the ileo-colic artery, dividing into two main branches. The first of these (1) passes distally in the free edge of the fold to the terminal part of the appendix. The other proximal branch (2) turns downward to the root of the appendix and the adjacent wall of the cæcum, aiding materially in holding the proximal upturned segment of the appendix in contact with the left cæcal sacculation.
The intermediate fold, short in its cæcal attachment, does not meet the dorsal vascular fold at any point, consequently the ileo-cæcal fossa is not limited caudad toward the root of the appendix. The conditions presented by this specimen correspond exactly to those found in the gorilla ([Fig. 457]) and in the human infantile preparation ([Fig. 563]).