196 



FRANKLIN PARADISE JOHNSON 



columnar in form than those of the gastric pits. Throughout 

 all these portions of the large intestine the cells on the crests 

 of the ridges differ from those between them. In the rectum 

 the epithelium is distinctly one-layered. On the crests of its 

 folds it presents a number of cells with clear protoplasm and 

 basal nuclei. These presumably are developing goblet cells. 



In the colon of an embryo of 58 mm. the epithelial tube is 

 found to be quite similar to that of the 55 mm. embryo just 

 described. It is slightly smaller throughout than in the previous 

 stage, which difference may in part be accounted for by the 

 different kinds of preserving fluids used. In the cephalic end 



Fig. 2 Cross section of the transverse colon of a human embryo of 58 mm. 

 X60. 



of the ascending colon the epithelial tube has now a diameter 

 of 0.38 mm. and shows numerous ridges and folds as seen in 

 figure 15. More caudally in the ascending colon the epithelium 

 is not so irregular as near the caecum. As seen in sections three 

 folds and one ridge are present. Figure 16 shows a model of 

 this portion of the intestine. It is to be noted that the tops 

 of the longitudinal folds are irregular in form. The diameter 

 of this region of the gut is about 0.36 mm., while the epithehum 

 averages about 0.050 mm. in thickness. 



The transverse colon of an embryo of 58 mm. shows six dis- 

 tinct folds, as seen in figure 2. A model of one half of the tube 

 of this region is represented in figure 17. The diameter of the 



