DEVELOPMENT OF THE LARGE INTESTINE 193 



ess and ascending colon three to four of these are present ; in the 

 transverse colon two to three ; in the greater part of the descend- 

 ing colon three; while in the remainder of the descending colon five 

 to six more irregular ones. These folds vary in height from 0.014 

 to 0.028 mm. The epithehum is thicker on their crests than 

 between them. It presents an appearance which is largely in 

 accordance with a condition which Patzelt ('83) has found in 

 the large intestine of the cat embryo. He describes two types 

 of cells. In the corners of the star-shaped lumen the cells are 

 short and broad, and have basal nuclei which stain intensely 

 with haemotoxylin. The cells of the second type are found on 

 the tops of the folds. They are longer, finely granular, and 

 somewhat denser. Their nuclei are long-oval or drop-shaped 

 and stain more intensely than those of the first type. The for- 

 mer groups of cells he states are the first anlagen of the Lieber- 

 kuhn glands; the latter of the villi. The epithelium of the large 

 intestine of the embryo under consideration (42 mm.) has been 

 described and pictured by Lewis ('11). The two types of cells 

 are found arranged in separate groups, but, however, are not 

 as distinct as those of the cat described by Patzelt. 

 • In the ascending colon of an embryo of 50 mm., the epithelial 

 tube has a diameter of about 0.23 mm., and shows four distinct 

 longitudinal folds. These are, as shown in figure 12, rounded 

 on their tops, and are of different heights, the largest measuring 

 about 0.06 mm. In the piece of ascending colon sectioned for 

 study, which measures about 0.7 mm. in length, the epithelial 

 tube changes but little in shape, the four distinct longitudinal 

 folds running throughout. The epithelium, which has an aver- 

 age thickness of 0.050 mm., is columnar, and, as seen in sections 

 ten microns thick, is apparently stratified, being composed of 

 two or perhaps three, layers of cells. The nuclei, which are 

 oval in shape, are all placed in a zone midway between the free 

 and basal surfaces of the epithehum, there being a clear zone 

 of protoplasm on either side. A definite cuticular border is 

 everywhere present on the free surface of the epithelium. Two 

 distinct types of cells are not visible. Outside of the epithehum 

 is a zone of loose mesenchyma which is bounded by a thin layer 



