DENELOPMENT OF THE RECTIAI 



23 



!''!■.. 





■.i^-C'." 



n 



trans, vil. f:$^^' ' A'", ^ '"-^^&Sj r| ' J'' 





int. 



lev. ani 



l.ano-rec. 





I .sin 





-. \ uif.sph. 



Fig. 1 Longitudinal section through the rectum of :i liuman embryo of 88 mm. 

 X 40 diameters. Between the ano-rectal line and the sinuous line is the zona col- 

 uumaris lined with stratified columnar epithelium. Below the sinuous line is the 

 zona intermedia. The ano-cutaneous line is not developed at this stage, ext. 

 sph., external sphincter muscle; gl.int., intestinal gland; int.sph., internal splim- 

 cter muscle; l.ano-rec, ano-rectal line; I. sin., sinuous line; ler.ani., levator ani; 

 m.m., muscularis mucosae; rtcs., rectal sinus; trans. vil., transitory villus of the 

 ampulla recti. 



