34 FRANKLIN PARADISE JOHNSON 



The rectum at birth has been studied from five different speci- 

 mens. Of these series 10.8 and 10.23 were cut sagittally, series 

 10.20, 10.21, and 10.22 were cut in cross sections. 



The form of the rectum is best seen in the latter two series. 

 Neither of these present any notable differences in form from that 

 of the 240 mm. embryo described above. As shown in a model 

 of series 10.22 (not figured) the primary and secondary folds cor- 

 respond very closely with those shown in figures 10 and 20. The 

 lumen and size of the tube, however, is somewhat smaller, owing 

 undoubtedly to less distention. Series 10.20 presents what ap- 

 pears to be a flattened and distorted condition of the whole pars 

 analis recti. However, as the preservation of this specimen is 

 poor, a description of it will be omitted. 



The form of series 10.21 is shown in figure 5. In 5 is repre- 

 sented a section through the lower portion of the ampulla showing 

 true intestinal glands and no villi. In C is seen a section through 

 the zona columnaris. The three primary and numerous second- 

 ary folds are quite distinct. Section D is through the upper part 

 of the zona intermedia. Several intramuscular glands, which 

 arise from the zona columnaris higher up, are seen just outside the 

 epithelial tube. In E is shown a section taken through the lower 

 portion of the zona intermedia. The sharp irregular folds have 

 given way to larger and more rounded ones. The three primary 

 folds terminate in this zone in a manner as described for the pre- 

 ceding stages. Section F shows numerous se])aceous glands and 

 hair follicles, and is therefore through the zona cutanea. 



The relations of the different zones is well shown in sagittal 

 series 10.8. The zona columnaris, like in the preceding stages, 

 is lined with a stratified columnar epithelium. The sinuous anal 

 line is distinctly marked by a sharp transition from the stratified 

 columnar epithelium to the stratified squamous epithelium. The 



Fig. 5 A, reconstruction of the lower part of the rectum of a full term fetus- 

 X 4. 5, C, D, E, F. Succepsive sections of the rectum taken at the levels as 

 shown in A. X 8. foll.pili., hair follicle; gl.int., intestinal gland; gl.inirm.', 

 intramuscular gland; gl.seh., sebaceous gland; s.col.ep., simple columnar epithe- 

 lium; str.col.ep., stratified columnar epithelium; sir.sq.ep., stratified squamous 

 epithelium. 



