14 FRANKLIN PARADISE JOHNSON 



Development of the anal glands 



Regarding the embryology of the anal glands in man, the work 

 of Herrmann alone is known to the writer. He asserts that the 

 intramuscular glands are present as small epithelial buds in an 

 embryo of 140 mm. In an embryo.of 190 mm. they have pene- 

 trated the internal sphincter, in which they end in small ampulla- 

 like swellings. At this stage the glands are not pro\'ided through- 

 out with lumens, but are in some places solid cords of cells. At 

 240 mm. they extend through the whole thickness of the internal 

 sphincter muscle and are complete canals. In the region of their 

 terminal swellings lymphoid tissue is already being laid down. At 

 birth they are quite similar to those of the adult. 



OBSERVATIONS 

 Early stages 



Under this heading are arbitrarily grouped stages up to 22.8 

 mm. when the first evidences of the columns of Morgagni are seen. 

 No attempt has been made to work out the early history of the 

 formation of the hind-gut and cloaca, for this has already been 

 thoroughly done by Keibel ('96), whose observations have been 

 recently confirmed by Pohlmann ('11). These observers show 

 clearly the relations of the hind-gut in its earlier stages to the 

 allantois, and of the rectum to the cloaca, and the division of the 

 cloaca into the rectum and the urogenital sinus. 



Observations on embryos of 7.5 mm. (H.E.C. 256) and 10 mm. 

 (H.E.C. 1000) have already been reported (Johnson '13). In 

 these stages the rectum has the form of a hollow tube, and in the 

 10 mm. embryo presents at its lower extremity a spindle-shaped 

 swelling. The cloaca is present but closed off from the outside by 

 the cloacal membrane. These observations are in accordance 

 with those of Keibel and Pohlmann, who state that the cloaca is 

 never open to the outside. 



In an embryo of 13.6 mm. (H.E.C. 839) the rectum presents a 

 large spindle-shaped swelUng. At the lower end of this swelling 

 the epithelial tube becomes much reduced in size, but just before 



