350 CHESTER H. HEUSER 



There are no glands present in any part of the intestine, but 

 between the vilh the epitheUal cells are in many places more 

 closely packed, more darkly stained, and of smaller size than 

 those of the villi. A group of these cells is shown in figure 18. 

 In corresponding regions of the two stages, the villi are taller 

 and more highly specialized in the pouch-young (cf. figs. 13 and 

 17). Of the loops in the older specimen the one at 7-8 in figure 

 16 has the largest lumen. Here the villi are much lower than 

 in the coils nearer the stomach, but the details of the mucosa 

 and of the other layers are very similar to those found in the 

 duodenum. The smaller coils have increased in size only slightly 

 and the villi are imperfectly formed in some of the limbs and 

 absent in others. The striking thinness of the external layers 

 of the intestine is more marked in the pouch-young than in the 

 embryo. This feature of the pouch-young is well illustrated by 

 the photographs (figs. 17 and 18). The relation of the mucosa 

 and the blood-vessels is again very intimate; the entire core of 

 each villus is occupied by a large sinus-like vessel. 



Large intestine 



In the embryo: The large intestine begins at its junction with 

 the small intestine, the point of origin being just below the 

 corpus of the stomach on the left side of the abdominal cavity. 

 From this point it swings gradually toward the midplane of the 

 body and leads a nearly straight course downward tb the cloaca. 

 The diameter of the large intestine is nearly the same throughout 

 its extent, being about equal to that of the most slender of the 

 coils of the small intestine. The caecum is a long slender blind 

 outgrowth from the large intestine immediately below the begin- 

 ning of this part of the gut. The caecum grows out at a sharp 

 angle and extends ventrally just beneath the stomach, so that 

 the blind end is seen in ventral views of the viscera (fig. 7) . 



The epithelial tube of the colon is small and laterally con- 

 stricted with the dorsal edge bent toward the left and the ventral 

 edge toward the right so that in cross-section it appears as a 

 widely opened letter S. Since the epithelial tube is small, the 



