366 THE ANATOMY OF THE HORSE. 



these epithelial cells are heaped up to form the cumulus or discus 

 proligerus, the cells of which surround the ovum. 



c. The Liquor Folliculi. — This is a fluid which fills up the remainder 

 of the cavity of the follicle. 



The Ovum is a typical animal cell. It consists of an outer envelope — 

 the zona pellucida ; protoplasmic cell-contents — the vitellus or yelk ; 

 a nucleus — the germinal vesicle ; and, within the nucleus, a nucleolous — 

 the germinal spot. 



The Graafian follicles vary greatly in size. The smallest are of 

 microscopic size, and differ from the larger follicles in having only a 

 single layer of cells in the membrana granulosa, and in having no liquor 

 folliculi. Follicles of intermediate size differ from the largest chiefly in 

 the small amount of liquor that they contain. These differences of size 

 represent different stages of development of the follicles, the largest 

 being the most mature. When mature, a follicle occupies a considerable 

 space in the substance of the ovary in the neighbourhood of the ovula- 

 tion fossa. Finally it bursts through the surface of the ovary, and the 

 ovum, along with the liquor folliculi and part of the membrana granu- 

 losa, escapes and is caught by the expanded extremity of the Fallopian 

 tube. The follicle then collapses, while it becomes in part filled with 

 blood from the vessels opened by the rupture of its wall. The rupture 

 then heals, and the follicle becomes converted into a yellowish body — 

 the corpus luteum. In the early stage of a corpus luteum the cells of 

 the membrana granulosa proliferate, while capillaries extend into it from 

 the wall of the follicle. Later on the blood-clot in the centre becomes 

 decolorised, and the granulosa cells become fatty ; and finally the 

 corpus luteum shrinks and disappears. 



The Parovarium, or the Organ of Rosenmuller. This a minute 

 body situated in the broad ligament, between the ovary and the 

 Fallopian tube. It consists of a number of short convoluted tubules 

 opening into a longitudinal tube, the latter representing the canal of 

 Gcertner in the cow. The parovarium is the homologue of the epididy- 

 mis of the male. 



The Fallopian Tubes, or Oviducts. The Fallopian tube is the duct 

 for the conveyance of the ova from the ovary to the uterus. In its 

 course between these two organs the tube passes in a flexuous manner 

 between the layers of a peritoneal fold which forms part of the broad 

 ligament. The ovarian extremity of the tube opens on the surface of 

 an expansion whose rim is cut into a few short fringe-like processes — 

 the Jimbrice. Part of the rim of this expansion is fixed to the under 

 surface of the ovary in front of the ovulation fossa. The upper surface 

 of the expansion is covered by a mucous membrane with delicate rugae 

 that converge from its rim to its centre, where it shows the minute 

 orifice of the tube — the ostium abdominale. The under surface of the 



