336 DR D. BERRY HART. 



These sections show well that the processes which bring about 

 the complete urinogenital sinus, bladder, etc., ;ire due to develop- 

 ment from above and below, as in sections 34-37 we have no 

 ■connection between urinogenital sinus above and the part 

 being formed from below. We have at this stage a real cloacal 

 arrangement, the urinogenital sinus and bowel opening into a 

 large undivided space — the cloaca. How has this arisen ? So 

 far as I know, the intermediate stage has not been found in the 

 human embryo, but from what Eetterer has figured in the rabbit 

 embryo (figs. 16 and 17), we may have an epithelial ectodermic 

 plug formed, pyramidal in section, with its apex towards the 

 lower portion of the urinogenital sinus to meet the coronal 

 partition of the primitive gut, and by the breaking down of 

 this centrally we get the condition of the 6 to 7 weeks' foetus 

 produced (fig. 18). 



We have now to consider how the permanent condition of 

 the pelvic organs in the adult is brought about. How is the 

 perineum formed ? This we now take up. 



The course of the changes described here is known in part 

 from human embryos, aided by a knowledge of what takes 

 place in the embryos of lower mammals, and also by a con- 

 sideration of certain rare malformations in the adult female 

 •due to defective cloacal changes. On this subject the most valu- 

 able papers are by Eathke, Reichel, von Rosthorn, Keibel, 

 Tourneux, and Eetterer. Eeichel in his paper describes a 

 case of a patient 25 years of age who was admitted to the 

 Klinik complaining of incontinence of feeces. Prior to her 

 marriage, three years before, her condition in regard to this 

 had been normal. On examination, anus, labia minora and 

 majora were found normal, but a fistula ran between the 

 rectum and the fossa navicularis, the external opening being 

 below the hymen. The perineum was short and badly developed. 

 The fistula was undoubtedly due to coitus. Von Rosthorn and 

 Caradec relate similar cases. In von Rosthorn's case the lower 

 end of the fistula admitted two fingers. 



Reichel gives a good account of the development bearing on 

 this particular point. He confirms Rathke's description in 

 1830 as to the closing of the cloacal opening. This happens as 

 follows : — 



