348 CHESTER H. HEUSER 



of the coils of the mtestine can be seen in a single section, as 

 shown in figure 12, where the great difference in the diameter of 

 the various loops is apparent. Numerous long villi are present 

 in the duodenum and first coils of the small intestine, as shown in 

 figure 12 at 1, 4, 5, '^y 8. In the slender loops 10, 11, and T2 

 there are no villi, but the mucosa is thrown into four or five folds. 

 The ductus choledochus enters the duodenum in limb 1 eight 

 sections (40m) below the section figured. Limb 5 of section 254 

 is shown at a higher magnification in figure 13. 



The low columnar cells of the mucosa rest upon a distinct 

 basement membrane. Definite cell-walls are usually made out 

 and the cuticular border ends abruptly in a narrow dense band, 

 bulging out in the middle part of the cell. Intercellular cement 

 lines are prominent in surface views of the tips, of the cells, and 

 terminal bars are therefore distinct. The nuclei, which are 

 located in the lower part of the cells near the basement mem- 

 brane, are usually spherical and contain one or two large nucleoli. 



The relations of vessels and the great difference in thickness of 

 the various layers are also indicated in figure 13. Numerous 

 vessels, as also in the earlier embryo (figs. 1 and 2), appear 

 beneath the mucosa, and the core of each villus is practically 

 filled by a large sinus-like blood-vessel. The outer layers of the 

 intestinal wall are very thin; the muscular coat is especially 

 delicate, consisting of a single, or in places, of a double row of 

 myoblasts. 



In the pouch-young: After birth, although the intrusive stomach 

 crowds the other viscera out of their former positions, the general 

 arrangement of the coils in the intestines is not fundamentally 

 disturbed. The large loops of the duodenum and the first loops 

 immediately following are similar to their former pattern. This 

 essential similarity in coils of the two stages was strikingly 

 illustrated by a dissection which was made of a formalin-fixed 

 pouch specimen of the same litter as the one shown in figure 6. 

 The coils of the intestine could be spread apart under the binoc- 

 ular microscope so that the various limbs and loops could be 

 compared with those found in the late embryo. As in the latter, 

 the duodenum had by far the largest caliber of any part of the 



