DEVELOPMENT OF THE LARGE INTESTINE 213 



as a whole is considerably thinned out. Owing to poor preser- 

 vation, however, it was not possible to determine the presence 

 of villi and folds. Measurements made are as follows: 



Total diameter of epithelial tube 5.5 x 14.5 mm. 



Perimeter, measured as before 34 . 7 mm. 



Thickness of mucosa 0. 16 mm. 



Thickness of outer coats 0,20 mm. 



Number of glands 269.0 



Number of glands per millimeter 7.7 



In a fetus of about seven months (premature birth) the ascend- 

 ing colon seems to be almost entirely devoid of villi and the 

 before-descrilDed folds. Although not modelled, it is plain to 

 see that the surface epithelium is for the most part, though not 

 entirely, level. At more or less regular intervals, it dips down 

 into the cylindrical intestinal glands. Measurements: 



Total diameter of epithelial tube 3.7 mm. 



Perimeter 18.5 mm. 



Thickness of mucosa 0.27 mm. 



Thickness of outer coats 0.54 mm. 



Number of glands 162 . 



Number of glands per millimeter 8.7 



Sections of the sigmoid colon show a similar condition as 

 regards glands. They are of an equal length and similarly dis- 

 tributed. 







Fig. 8 Cross section of the mucosa of the transverse colon of a human embryo 

 at birth. X 60. 



In a fully developed fetus at birth (fig. 8), a condition is reached 

 in which the villi have entirely disappeared. A model of a por- 

 tion of the epithelium of the transverse colon is shown in figure 

 25. As seen from the model, only glands are present, the open- 

 ings of which appear irregular when viewed from the lumen 



