DEVELOPMENT OF THE RECTUM 9 



The 'ano-cutaneous' line is drawn at the point where the anal 

 epitheUum passes over the stratified squamous type (Robin and 

 Cadiat's " Hgne sinueuse")- Below this line is the zone ''cutanee 

 peri-anale" (''zone eutanee lisse" of Robin and Cadiat). In 

 agreement with the descriptions set forth by Robin and Cadiat, 

 Herrmann says this region is deprived of hairs, sebaceous and 

 sweat glands. Its epithelium is stratified polyhedral, composed 

 of six to eight layers of cells, and differs from that of the skin by 

 the absence of indented cells and a cornified covering, for al- 

 though the superficial cells are somewhat flattened, they have not 

 a lamellar form. The nuclei are clear and the cell bodies finely 

 granular and stain the same as the underlying cells. Neither a 

 stratum corneum nor stratum lucidum is present. 

 ■ The anal mucous membrane proper, that is, the zone between 

 the ano-rectal and ano-cutaneous lines, is thrown into folds 

 (columns of Morgagni) between which lie rounded sinuses. Ex- 

 tending outward from these sinuses are recesses of a second type, 

 narrow slit-like cavities which reach almost to the internal 

 sphincter. A third type of sinus extends from the secondary type 

 in the form of branched tubules. These, which he calls the 

 ''intramuscular sinuses" ("special acinose glands") are dealt 

 with below. The anal mucosa is covered by an epithelium which 

 is made up of several layers of polygonal cells but the superficial 

 cells are of the prismatic type. The protoplasm of these pris- 

 matic cells is transparent and only slightly granular and not 

 readily staining. 



He states further that it is a general rule that the stratified 

 polygonal epithelium covers the more elevated parts (columns of 

 Morgagni), while the prismatic type is found in the depths of the 

 mucosa, in other words, "those parts which are not exposed to 

 pressure and mechanical effects." 



Ball ('94) states that the "white line of Hilton" is the ano- 

 rectal line of Herrmann, but since he says it occurs at the level of 

 the semilunar valves, he undoubtedly means Herrmann's ano-cu- 

 taneous line. Birmingham ('09) uses the terms "white line of 

 Hilton" and "ano-cutaneous line of Herrmann" synonymously. 



