1. The general shape and trend of the fœtal cæcum is preserved. The pouch turns sharply to the left, carrying the apex with the root of the appendix upward toward the ileum, the appendix itself being frequently placed under cover of the terminal coil of the small intestine (schema, [Fig. 509], IIb).

Fig. 519.—Human adult (Smith’s Sound Eskimo). Ileo-colic junction and cæcum. (Columbia University Museum, No. 59/1483.)

Fig. 520.—Human adult. Ileo-colic junction and cæcum. (Columbia University, Study Collection.)

Fig. 521.—Human adult. Ileo-colic junction and cæcum. (Columbia University, Study Collection.)   Fig. 522.—Human adult (Smith’s Sound Eskimo). Ileo-colic junction and cæcum. (Columbia University Museum, No. 56/1571.)

The apex of the cæcal pouch is either conical, narrowing gradually toward the root of the appendix (Figs. 520 and 521), or blunt and more sharply defined against the appendix (Fig. 522). Mr. Treves encountered this “persistent fœtal type” in two per cent. of his series.

Fig. 523.—Human adult. Ileo-colic junction and cæcum; dorsalview; dried preparation. (Columbia University Museum, No. 200.)

Fig. 524.—Human fœtus at term. Ileo-colicjunction and cæcum; ventral view. (Columbia UniversityMuseum, No. 1717.)

 

Fig. 525.—Same preparation as Fig. 524;dorsal view.

The cæcum is frequently sharply bent on itself in making the turn upward and to the left, resulting in a deep indentation of the concave border and producing a corresponding projecting fold in the interior of the pouch (Fig. 523). The ventral longitudinal muscular band follows the crescentic sweep of the cæcum to the root of the appendix.

Figs. 524a and 525b, representing the cæcum of a fœtus at term in the ventral and dorsal view respectively, show very clearly the arrangement of the fœtal pouch from which the adult type with sharp angular bend is derived. This type of adult cæcum is found in certain of the anthropoid apes.