10 FRANKLIN PARADISE JOHNSON 



Development of columns, sinuses and valves 



Regarding the development of these structures very Uttle has 

 been written. The paper which deserves most credit is that of 

 Herrmann ('80). His observations begin in an embryo of 85 mm. 

 At this stage he states that the mucosa of the anal region forms a 

 zone about 1 mm. in height, and contains on the sides excava- 

 tions which are divided into several compartments by longitudi- 

 nal folds. These folds of mucous membrane form the columns 

 of Morgagni, and mark the places where the muscular columns 

 are to develop. The epithelium is stratified prismatic, composed 

 of two to three layers of cell's, and is about 0.025 to 0.030 mm. 

 thick. The peri-anal cutaneous zone is covered by a stratified 

 squamous epithelium of six to eight layers of cells, but shows no 

 traces of hairs or glands. At 140 mm. the longitudinal folds are 

 more numerous and in places are no more than 0.1 mm. from the 

 internal sphincter muscle. In the epithelium of the peri-anal 

 zone, in its outer part, hair follicles and sebaceous glands are be- 

 ginning to appear. Sweat glands are present as tortuous cyliYi- 

 drical tubes of epithelium which are greatly swollen at their 

 extremities. 



In an embryo of 190 mm. the muscularis mucosa is present in 

 the region of the rectal ampulla, but is absent from the anal 

 region. In neither the rectal or the anal mucosa are solitary 

 nodules present. At 210 mm. the anal mucosa has grown to a 

 height of 2.5 mm. and has an epithelium of 0.04 to 0.05 mm. in 

 thickness. At birth the anal region has a height of 3.5 mm. The 

 muscularis mucosae is completely formed and is prolonged in 

 several strands which extend down into the rectal columns. 

 Finally in an infant of two years, he says, are to be found the 

 identical disposition of all structures which are found in the adult, 

 only with reduced dimensions. 



Ball ('94) regards the semilunar valves as vestigial remnants. 

 Re says: ''I think it may with tolerable confidence be asserted 

 that the anal valves are vestigial remains of the anal plate, the 

 rest of which has disappeared in the process of development." 

 No evidence, however, is given in support of this assumption. 



