370 THE ORGANS 



remains of the embryonal mesonephros, the former of its posterior 

 segment, the latter of its middle segment. 



The Oviduct 



The oviduct or Fallopian tube is the excretory duct of the ovary, 

 serving for the transmission of the discharged ovum from ovary to 

 uterus. Although there is no sharp demarcation between them, 

 it is convenient to divide the tube into three segments: (i) The 

 isthmus, beginning at the uterus and extending about one-third the 







r-c 111 ^'-c^'jjiv, 



—a 



n 







'=? — • "•'■? ^ ^"^ ' 



Fig. 262. — Cross Section of Oviduct near Uterine End. a, Mucous membrane; h, 

 circular muscle coat; c, longitudinal muscle coat; d, connective tissue of serous coat. 

 (Orthmann.) 



length of the tube; (2) the ampulla, about twice the diameter of the 

 isthmus, and occupying somewhat more than the middle third; 

 and (3) the fimbriated or ovarian extremity. 



The walls of the oviduct consist of three coats: (i) Mucous, (2) 

 muscular, and (3) serous (Figs. 262 and 263). 



The mucous mernbrane- presents numerous longitudinal foldings. 

 In the embryo four of these folds can usually be distinguished, and 

 these are known as prii\iary folds. In the adult many secondary 

 folds have developed upon the primary, especially in the ampulla 

 and fimbriated extremity where the folds are high and complicated 

 (Fig. 263). The epithelium lining the tube is of the simple columnar 

 ciliated type, "and completely covers the foldings of the mucous mem- 



