STRUCTURE OF THE TUBA. 501 



laminar, partly conical, or form low ridges. The epithelium 

 consists of tolerably high columnar and ciliated cells. The 

 matrix of the folds is a dense, very vascular fibrous plexus. 

 The muscular layer of the mucous membrane is made up of 

 longitudinal muscular fibres. 



At the ampulla the adventitia and muscular layer present 

 the same relations, but the mucous membrane is beset with 

 many complicated folds that suggest it has to perform a 

 different function. These folds project farther into the lumen 

 of the canal than in the isthmus, and often appear to, and 

 sometimes actually do r coalesce with those of the opposite side. 

 These folds often have secondary folds upon them, which again 

 branch, giving to the whole an arborescent aspect. Simple 

 unbranched folds also occur, arranged in close apposition with 

 each other, which have led several authors (Bowman, Hennig) 

 to admit the presence of glands in the mucous membrane of 

 the oviduct. It may however easily be demonstrated in 

 longitudinal sections that no glands exist in the oviducts of 

 Man and Mammals. 



As regards the minute anatomy of the fimbria, they are 

 composed of the same elements as the other parts of the 

 oviduct, of which they are to be regarded as the direct con- 

 tinuations. They are exceedingly vascular. 



In the Fowl the external investing membrane and the sub- 

 jacent circular muscular layer are arranged as in Man. The 

 folds of the mucous membrane throughout the whole length 

 of the oviduct are unbranched, and consist of a finely fibrillated 

 plexiform tissue, in which cells usually of a rounded form are 

 distributed, and increase in numbers towards the epithelium. 

 In the centre of the fold is a vascular trabecula of connective 

 tissue, which gives off branches on all sides into the substance 

 of the fold, producing by their intercommunications the above- 

 mentioned finely fibrillated plexus. At the apex of the fold 

 the connective-tissue trabecula disappears, having exhausted 

 itself by giving off successive branches into the interior. The 

 epithelium is composed of many tiers of columnar and ciliated 

 cells. The folds vary in length. 



The structure of the oviduct in Bufo cinereus is quite differ- 

 ent ; for whilst in Mammals and Birds glands are never present, 



