526 THE REPRODUCTIVE SYSTEM 



somewhat in its several portions. In the isthmus it is relatively smooth 

 and usually presents four longitudinal ridges which have few secondary 

 or accessory folds ; in the ampulla the mucosa is greatly folded, the pri- 

 mary rugas possessing small secondary folds which extend in all direc- 

 tions, and by their very complexity nearly obliterate the otherwise broad 

 lumen. In the fimbriated portion the folds of the mucosa are continued 

 into the fimbria?, at the margin of which the columnar ciliated epithe- 

 lium of the oviduct becomes directly continuous with the serous mesothe- 

 lium of the peritoneum investing the outer surface of the tube. 



The mucosa is lined by columnar epithelium, arranged either in a 

 simple or pseudo-stratified manner, the greater portion of whose cells 

 are provided with cilia. The ciliary motion is directed toward the uterus. 

 The epithelial layer covers all the folds of the mucosa and, extending 

 deeply into the crevices, forms invaginations which, in transections of 

 the tube, simulate glandular structures. There are, however, no true 

 secreting glands in the oviduct. Here and there groups of non-ciliated 

 cells with clear cytoplasm occur among the more numerous ciliated cells 

 of the mucosa. 



The epithelium rests upon a thin homogeneous basement membrane 

 beneath which is a tunica propria consisting of a cellular type of connec- 

 tive tissue. Many of the connective tissue cells are of fusiform shape, 

 and, unless specially stained or carefully examined, they closely resemble 

 smooth muscle cells. The mucosa, however, contains no muscle except at 

 the bases of the largest folds, into which occasional fibers from the adja- 

 cent muscular coat penetrate. 



The muscular wall of the oviduct is formed by two layers of 

 smooth muscle a broad inner circular layer, and an outer longitudinal 

 coat, which is very unequally developed at different portions of the cir- 

 cumference, but is relatively thin in all parts, and is entirely wanting at 

 frequent intervals. The outer layer is usually broadest at the free mar- 

 gin of the oviduct and at its opposite side where the tube is attached to 

 the broad ligament. The inner circular fibers are more or less obliquely 

 disposed, and, toward the mucosa, the muscular bundles fuse insensibly 

 with the cellular connective tissue of the mucous membrane. In gen- 

 eral the inner circular layer is thickest at the isthmus and thinnest at 

 the infundibulum, while the longitudinal layer is thickest toward the 

 fimbriated end. 



The serous coat of the oviduct is continuous with the peritoneum. 

 It consists of an outermost layer of mesothelium which rests upon a sub- 

 epithelial layer of connective tissue, by which it is firmly united to the 



