DEVELOPMENT OF THE LARGE INTESTINE 219 



At 65 mm. the base of the vermiform process measures 0.45 

 to 0.54 mm. in diameter. Its epithehum is now provided with 

 distinct villi which resemble those found in the ileum and ascend- 

 ing colon of the same stage. Followed distalward the vermi- 

 form process becomes somewhat smaller, but even to its end, 

 villi are present. In some places they appear to be forming from 

 longitudinal folds. The epithelium is everywhere simple colum- 

 nar and has a thickness ranging from 0.028 to 0.042 mm. in 

 thickness, depending whether measured on tops of the folds or 

 between them. The large number of goblet cells present is 

 striking, there being by far a greater number in the vermiform 

 process than in the small or large intestine. 



In an embrj^o of 88 mm. the diameter of the vermiform proc- 

 ess at its base is about 0.45 mm. Numerous villi of about the 

 same size as those in the lower part of the ileum at this stage 

 (0.25 to 0.27 mm. in height) are found. The glands have begun 

 to appear and in places where they are cut in cross section they 

 show small round lumina. Toward its tip the villi are distinct, 

 but shorter (0.11 mm. high). Some are in the form of longi- 

 tudinal folds (fig. 26). Glands are in most places very small, 

 but their beginnings are everj^vhere visible. 



The epithelial tube of the base of the vermiform process in 

 an embryo of 110 mm. has a diameter of about 0.70 mm. Both 

 glands and villi are distinct, but the former are as yet very rudi- 

 mentary. In most places they are, as well as can be determined 

 from cross and longitudinal sections, 0.09 to 0.11 mm. in length. 

 The villi are shorter than those found in the base of the vermi- 

 form process of the preceding stage, being only 0.14 to 0.16 mm. 

 in height. Goblet cells are again very numerous. The distal 

 end has a diameter of 0.77 mm., being slightlj^ greater than its 

 proximal portion. The villi are again shorter (0.11 to 0.13 

 mm.) than those found above, but somewhat longer than those 

 found in the same portion of the vermiform process of the pre- 

 ceding embrj^o. The glands are approximately the same length 

 as before. The extreme tip is rounded in shape, and is provided 

 with villi and glands of the same type as those on the side walls. 



