. The development of the human body : a manual of human embryology. Embryology; Embryo, Non-Mammalian. THE INTESTINE 305 primary coils become apparent its point of attachment lies in the region of the sixth coil. As a rule, the caliber of the stalk does not increase proportionally with that of the intestine, and eventually its embryomic portion disappears completely. Occasionally, how- ever, this portion of it does partake of the increase in size which occurs in the intestine, and it forms a blind pouch of varying length, known as Meckel's diverticulum (see p. 113). The ccecum has been seen to
. The development of the human body : a manual of human embryology. Embryology; Embryo, Non-Mammalian. THE INTESTINE 305 primary coils become apparent its point of attachment lies in the region of the sixth coil. As a rule, the caliber of the stalk does not increase proportionally with that of the intestine, and eventually its embryomic portion disappears completely. Occasionally, how- ever, this portion of it does partake of the increase in size which occurs in the intestine, and it forms a blind pouch of varying length, known as Meckel's diverticulum (see p. 113). The ccecum has been seen to arise as a lateral outgrowth at a time when the intestine is first drawn out into the umbilicus. During subsequent development it continues to in- crease in size until it forms a conical pouch arising from the colon just where it is joined by the small intestine (Fig. 186). The en- largement of its terminal portion does not keep pace, however, with that of the portion near- est the intestine, but it becomes gradually more and more marked off from it by its lesser caliber and gives rise to the vermiform ap- pendix. At birth the original conical form Fig. 186.—caecum of of the entire outgrowth is still quite evident, B „ . *°'3 0 ^ c, Colon; 1, ileum. though it is more properly described as funnel- shaped, but later the proximal part, continuing to increase in diam- eter at the same rate as the colon, becomes sharply separated from the appendix, forming the caecum of adult anatomy. Up to the time when the embryo has reached a length of 14 mm., the inner surface of the intestine is quite smooth, but when a length of 19 mm. has been reached, the mucous membrane of the upper portion becomes thrown into longitudinal folds, and later these make their appearance throughout its entire length (Fig. 187). Later, in embryos of 60 mm., these folds break up into numbers of conical processes, the villi, which increase in number with the development of the intestine, the new villi appear
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