3. Finally, in about four per cent. to five per cent., adult caeca, the reduction of the wall to the left of the root of the appendix, between this point and the ileo-colic junction, is complete. The entire caecal pouch is formed by the dilated right wall between the ventral and dorsolateral muscular bands. The ventral band terminates at the lower border of the ileo-colic junction, from which the appendix appears to arise, indicating the original apex of the foetal caecum (schema, Fig. 509, _II^e_). This type is illustrated in the specimens shown in Figs. 533 and 534. [Illustration: FIG. 532.--Human infant, Ileo-colic junction and caecum, with secondary terminal sacculation. (Columbia University Museum, No. 1632.)] [Illustration: FIG. 533.--Human adult. Ileo-colic junction and caecum; dorsal view; dried preparation. (Columbia University Museum, No. 124.)] [Illustration: FIG. 534.--Human adult. Ileo-colic junction and caecum; ventral view; dried preparation. (Columbia University Museum, No. 14.)] =III. Adult Caeca in Cases of Absence of the Appendix.=--A few instances of congenital absence of the appendix have been observed. A. v. Haller[9] describes the condition in the following words: "Defuisse visa est in homine appendicula, ut tuberculum minimum superesset." [9] A. v. Haller, Elements physiologiae, Tom. 7, Liber 24, Sect. 3. Fr. Arnold,[10] without describing any individual case, states that "very rarely the appendix is entirely wanting." [10] Fr. Arnold, Handbuch der Anat. d. Menschen. 1847. II. Bd., cloth, p. 84. E. Zuckerkandl,[11] reports having observed one case of absence of the appendix. [11] E. Zuckerkandl, "Ueber die Obliteration des Darmfortsatzes beim Menschen." Anat. Hefte XI. (Bd. IV., Heft 1), 1894, p. 107. J. D. Bryant,[12] reports a case in which he operated for appendicitis but found "absolutely no appendix." "The point of tenderness was found to be a glandular growth located posterior to the usual site of the appendix." [12] N. Y. Med. Journal, Vol. LXIX., No. 14, p. 508. [Illustration: FIG. 535.--Human adult. Ileo-colic junction and caecum; absence of appendix. (Columbia University Museum, No. 1077.)] [Illustration: FIG. 536.--Human adult. Ileo-colic junction and caecum, hardened _in situ_; absence of appendix. (Columbia University Museum, No. 715.)] Two instances of this variation are shown in Figs. 535 and 536, taken from preparations in the Morphological Museum of Columbia University. In both careful examination of the external as well as of the mucous surface of the caecum demonstrated the entire absence of the appendix, and the subjects from which they were obtained presented no scars or other evidences of operative removal or of pathological processes. They are both, therefore, authentic instances of complete congenital absence of the appendix, not of so-called retro-peritoneal or hidden appendix.[13] [13] Cf. Quain.