32 



FRANKLIN PARADISE JOHNSON 



In another embryo of about the same age, (length 245 mm.) a 

 few noteworthy differences were observed. The ampulla and 

 pars analis were both distended with meconium. The series of 

 sections includes the whole of the zona cutanea, the zona inter- 

 media, but only a portion of the zona columnaris. This latter, 



gLintrm. 



lonq.m. 



m. lev. ani 



Fig. 4 Portion of a cross section of the pars analis recti of a human embryo of 

 24o mm. X 30. Between .r and x' is a rectal sinus, lined with a stratified 

 columnar epithelium. It belongs to the zona columnaris. The remainder of the 

 surface epithelium is stratified squamous, and belongs to the zona intermedia. 

 circ.m., and long.m.. circular and longitudinal layers of the muscularis; ^fLr/i^rw., 

 intramuscular gland ; ni.ler.atiiAcvaior ani muscle; rcc.cul.. rectal column; x and 

 x', sinuous line. 



while its lumen is relatively large, shows distinct folds of its 

 mucous membrane quite similar to those of the other stages 

 described. 



The epithelium lining the tube of the uppermost section of the 

 series is for the most part stratified columnar, although it is strat- 

 ified squamous on the tops of the larger infoldings and again in 



