AND ITS APPENDAGES. 645 



here still imperfectly closed, leaving a wide opening at , b, where 

 the integument of the foetus becomes continuous with the com- 

 mencement of the amniotic membrane. The intestine makes at 



Fig. 241. 



Formation of ALIMENT ART CAXAL. n, b. Commencement of amnion. c, c. Intestine, d, 

 Pharynx, e. Urinary bladder. / Allantois. g. Umbilical vesicle, x. Dotted line, showing the 

 place of formation of the oesophagus. 



first a single angular turn forward, and opposite the most promi- 

 nent portion of this angle is to be seen the obliterated duct, which 

 forms the stem of the umbilical vesicle, (g.) A short distance below 

 this point the intestine subsequently enlarges in its calibre, and the 

 situation of this enlargement marks the commencement of the 

 colon. The two portions of the intestine, after this period, become 

 widely different from each other. The upper portion, which is the 

 small intestine, grows mostly in the direction of its length, and 

 becomes a very long, narrow, and convoluted tube-: while the lower 

 portion, which is the large intestine, increases rapidly in diameter, 

 but elongates less than the former. 



At the point of junction of the small and large intestines, a late- 

 ral bulging or diverticulum of the latter shows itself, and increases 

 in extent, until the ileum seems at last to be inserted obliquely into 

 the side of the colon. This diverticulum of the colon is at first 

 uniformly tapering or conical in shape ; but afterward that portion 

 which forms its free extremity, becomes narrow and elongated, and 

 is slightly twisted upon itself in a spiral direction, forming the 

 appendix vermiformis ; while the remaining portion, which is con- 

 tinuous with the intestine, becomes exceedingly enlarged, and forms 

 the caput coli. 



The caput coli and the appendix are at first situated near the 



