200 FRANKLIN PARADISE JOHNSON 



creasing in length, the viUi are decreasing in height. In the 

 subsequent stages of development, the villi become always lower 

 and lower, so that it is now possible to say that the transitory 

 villi reach their maximum height in embryos between 110 mm. 

 and 140 mm., probably between 110 mm. and 120 mm. 



In that portion of the ascending colon adjacent to the colic 

 valve, shorter villi are found (0.14 to 0.18 mm. in height), which 

 are also lower than those in the ileum (0.27 to 0.36 mm.). Higher 

 up in the ascending colon the villi are of about the same size, 

 while the glands are 0.13 to 0.18 mm. in length, and in the begin- 

 ning of the ascending colon, a few enlarged glands, such as are 

 present in the vermiform process, are found. As regards A'illi 

 and glands, the descending colon is quite similar to the trans- 

 verse colon. In the sigmoid colon the villi are longer (0.18 to 

 0.27 mm.); in the rectum (0.18 to 0.36 mm.). Everywhere, 

 however, the glands remain about the same length as those 

 of the transverse colon. The epithelium is also quite similar 

 throughout the whole colon. It is high columnar in the glands, 

 lower on the sides, and lowest on the apices of the villi. Goblet 

 cells are extremely numerous everywhere, being more abundant 

 in the glands than on the villi. 



Effects of distention caused by a storing up of meconium 



A marked difference in the thickness of the mucosa is found 

 between the transverse colon of an embryo of 187 mm. and that 

 of the same portion of the intestine of an embryo of 190 mm. 

 (Compare figs. 6 and 7). That of the former is 0.36 mm. in 

 thickness, while that of the latter is only 0.16 to 0.20 mm., the 

 first being about twice the thickness of the second. The ques- 

 tion arises, how is this variation to be accounted for? It is 

 to be noted that the portion of intestine of the 190 mm. embryo 

 examined was filled with meconium, thereby extending its walls 

 and increasing the size of its lumen. The total diameter of 

 its epithelial tube is 4.2 mm., in comparison to 2.3 mm. in the 

 187 mm. stage. These measurements show only that the epi- 

 thelial tube is extended in the older stage, but they do not show 



