342 DR D. BERRY HART. 



hymeneal orifice — is formed. Thus the hymen is formed ly a 

 special lulhous development of the loiver ends of the two Wolffian 

 ducts aided hy an epithelial involution from heloiv of the cells lin'my 

 the urinogeniial sinus (fig. 20). 



Tlie hymen bilamellatus described by Schaeffer at the fifth 

 month is probably due to the persistence of the upper and lower 

 margins or edges of the bulbs, and disappears in the more 

 advanced foetus. Schaeffer's statement is: " Jeder Hymen 

 wird mehr oder weniger deuthch im 5 Monate als bilamellatus 

 angelegt." I have not, however, as yet had an opportunity of 

 examining this transitional form. 



The whole of the developmental changes might be summed up 

 now as follows : Formation of primitive gut, seen in embryos of 

 20th-23rd day (fig. 1); division of primitive gut into bladder 

 (with urinogenital sinus) and rectum, and withering of end-gut 

 about 20th-30th day (fig. 5); communication of bladder and 

 rectum with exterior (formation of cloaca) by breaking down of 

 hypothetical plug (in human species) before sixth week (figs. 16, 

 17, 18); closure of cloaca by Eeichel's Analhocker and for- 

 mation of perineum, 7th-Sth week: urinogenital sinus with 

 Milllerian ducts related to it and Wolffian ducts opening into 

 it, no anus, at 8th-9th week; hymen formed, anus formed, 

 preputium clitoridis in course of formation, Milllerian vagina 

 being relined, and uterus now single ; 3rd to 4th month 

 (figs°20, 21). 



These periods are only approximate. An excellent table is 

 given by Wendeler, and Nagel's papers should be consulted for 

 his views as to the formation of the perineum. 



IV. The Structure and Origin of the Adult Vagina. 



So far as the structure of tlie vagina in the adult is concerned, 

 I wish to direct attention only to two points — viz., 



(a) The relations of the normal hymen. 



(h) The naked-eye arrangement of the vaginal rugcc and 

 columns. 



I shall then discuss the Anlage, or fundamental origin of the 

 vagina. 



