THE ORGANS OF DIGESTION. 



279 



permanent position in front of the right kidney and inferior 

 vena cava. The caecum thus comes to be situated in front of 

 the right kidney, near the gall-bladder, and there it remains 

 until about the time of birth, when both the caecum and 

 ascending colon undergo a gradual migration towards the 

 right iliac fossa. The cause of this migration is not known, 

 but it occurs only in animals adapted to the upright posture. 

 Thus the attachment of the ascending meso-colon is formed by a 

 secondary adhesion to the parietal peritoneum during the migra- 

 tion of the colon and caecum. The appendix, during . the 

 migration, may be caught behind the colon ; it is then lodged and 

 fixed in the ascending meso-colon. 



great oment. 



spl.flex. 

 duodeno-jej. fossa 



sup. mes. art. 



■left colic artery 



pre-art. part mes. ' ^^(^m^L '"/■ mesent 



mter-sig. fossa 



sigmoid artery 



Fio. 226.— To show the Kotation of the Intestinal Loop and Formation of the 

 Duodenojejunal Fossa. 



The Appendix. — At first and until the third month, the caecal 

 diverticulum is of the same calibre throughout, but from the 

 third month onwards, the appendix remains small while the 

 caecum grows, keeping pace in diameter with the colon. At 

 birth the appendix is still the tapered apex of the caecal diverti- 

 culum (Fig. 224), but during childhood, an outer, or an inner, 

 sacculation, or both together, arise in the fundus of the caecum 

 and thrust the appendix backwards and to the left into an 

 asymmetrical position. 



Although a distinctly marked appendix is only seen in man, 

 the anthropoids, lemur, and opossum, still a corresponding 



