PLATE 7 



EXPLANATIOX OF FIGURES 



21 Lower portion of the primary fold of a human embryo of 135 mm. X 72. 

 gl.intrm., intramuscular gland; sc.f., secondary fold; tub., tubules; x, marks the 

 point where the gland penetrates the internal sphincter muscle. 



22 Intramuscular gland. Human embryo of 245 mm. X 72. a., acinous- 

 like ending; ep.w., epithelial wall. 



23 Branched intramuscular gland. Human embryo of 245 mm. X 72. a., 

 acinous-like termination; amp., ampulla of gland; br., branch; ep.w., epithelial 

 wall. 



24 Sagittal section through the pelvis at birth. X 1. b.w., body wall; bid., 

 bladder; C.I., 1st coccygeal vertebra; ext.sph., external sphincter muscle; La., 

 levator ani muscle; pl.tr., plica transversalis recti; rec.a., rectal ampulla; S.I., 

 1st sacral vertebra; sym.p., symphysis pubis; z.col., zona columnaris; z.int., 

 zona intermedia. 



25 Sagittal section through the lower part of the rectum. X 6. a.v., anal 

 valve; r.c, rectal column; rec.a., rectal ampulla; sin., rectal sinus; z.col., zona 

 columnaris; z.int., zona intermedia. 



56 



