DEVELOPMENT OF THE LARGE INTESTINE 209 



colon the submucosa, the muscularis, and the serosa together 

 measure about 0.24 mm., the distended one, 0.13 mm. 



From the above given figures, the effects of distention, caused 

 by a storing up of meconium in the large intestine may be enu- 

 merated as follows: (1) an increase in the diameter of the epi- 

 thelial tube; (2) an increase in the actual surface on which the 

 basal ends of the glands lie; (3) a decrease in the thickness of 

 the mucous membrane as a whole; (4) a decrease in the length 

 of the glands and an increase in their width; (5) a more marked 

 decrease in the height of the villi and an increase in their width 

 (6) a spreading apart of the glands and of the villi; and (7) a 

 decrease in thickness in the outer coats of the intestine. 



The above results led to the question as to what effect dis- 

 tention would have upon the intestine of an adult. The small 

 intestine of a guinea-pig was experimentally distended with 

 normal salt solution and fixed and hardened in that condition. 

 Although the results of this and other experiments may be found 

 in the following paper, it may be said here, that the results 

 obtained are largely in accordance with those just described in 

 the meconium-filled intestine of the human embryo. 



Because of the above described effects of marked distention 

 of the large intestine, it has been considered necessary, for the 

 sake of comparison, to select only non-distended portions of the 

 colon for modelling. In the case of the embryo of 190 mm. 

 the sigmoid colon was chosen, for while this region contains 

 meconium, there is no distention. This is made evident by the 

 presence of longitudinal or oblique folds of the mucous mem- 

 brane, and by the following measurements as compared with 

 those of the transverse colon of the same embryo: diameter of 

 intestine 3.4 mm.; thickness of mucous membrane 0.34 mm.; 

 thickness of outer intestinal coats, 0.23 mm. Figure 22 shows 

 the epithelium of this region of the intestine in surface view. 

 The villi have dwindled down until they appear merely as irregu- 

 lar knobs which are joined together at their bases in the form 

 of ridges. These ridges are of various lengths but all are of 

 about the same thickness. They run in different directions and 

 anastomose with one another, thus marking the surface of the 



