IXTERXAL ana AN S OF GENERATIOX. 40 



sublumbar region, behind the Fallopian tubes and the kidneys, among 

 the convolutions of the intestines, thouj^'h sometimes their position is 

 altered. In four instances in the Pig they have been found in the 

 perineal region, occupying small cavities analogous to the scrotum of 

 the male. ' Smooth externally, each ovary shows in the middle of its 

 upper portion a more or less oblique, but deep fissure, resembling the 

 hilus of the kidney, and which gives attachment to the pavilion of the 

 Fallopian tube. Each ovary is suspended at the anterior border of the 

 broad ligament, and is also sustained in situ by the vessels passing to 

 and from it, as well as by a small cord of non-striated muscular fibres 

 called the li(jamcnticm orarii, which connects it with the uterus. 



The structure o( the ovary comprises a serous and fibrous membrane, 

 the proper tissue of the ovary, and the Graafian vesicles embedded in it. 

 The serous membrane is continuous with the broad ligaments — is, in 

 fact, a peritoneal tunic which entirely envelops it, adhering closely to 

 the covering beneatii. This is the tunica albu(ji)iea—& dense resisting 

 membrane similar to the structure enveloping the testicle, and sending 

 lamellar prolongations into the substance of the ovary. 



The proper tissue or stroma of the ovary is solid and hard, and has a 

 speckled-grey tint. It is divided into two layers, which are distinct in 

 appearance and structure. The medullary layer is nearest the hilus, 

 and is somewhat red and spongy ; it is formed by the intercrossing of 

 connective tissue, non-striated muscular fibres, and by a large number 

 of vessels which radiate fi'om the centre towards the periphery of the 

 organ and nerves. The cortical layer has connective tissue for its basis ; 

 it is not very vascular, but it contains in its substance the Graafian 

 vesicles or follicles, and for this reason is named the oviijcnic layer. 



These Graafian vesicles are generally in various stages of develop- 

 ment ; the smallest are situated beneath the tunica albuginea, and they 

 descend towards the deeper layer, increasing in volume as they do so. 

 When they have reached their period of full growth, they are filled with 

 a transparent, citron-coloured fluid, and the ovigenic layer being in- 

 capable of containing them, they form a more or less considerable 

 prominence on the sui-face of the ovary. A Graafian vesicle, when 

 perfect, is composed of an envelope and its contents. The envelope 

 comprises two tunics — a fibrous membrane (tunic of the ovisac), which 

 is continued externally with the stroma of the ovary, and internally is 

 rich in bloodvessels ; an inner (ovisac), formed by a smooth membrane 

 which derives its bloodvessels from the latter ; it is lined by an epithe- 

 lial or granular membrane (tunica i/ranulosa), composed of round or 

 polygonal granular cells. At the bottom of the vesicle this epithelium 

 forms an aggregation (the cumulus, or discus proliijcr), in the centre of 

 which exists the ovum or ovuluvi of mammalia. The contents of the 

 vesicle is a yellowish, transparent, albuminous mass, that becomes 

 reddened by an admixture of blood when the vesicle ruptures. 



The ovulum, ovule, or ovum, is a small cell imbedded in the cumulus, 

 and surrounded by an amorphous, thick, white membrane, which has 

 been designated the zona pcllucida ; within this membrane is a granular 



' A remarkable, if not unique, cane of displacement of the ovarie* i<» recorded by 

 M, Dupmt, in the Journal df» Vitirinair>t <Ih .}fi'li for 1869. In four female I'ip«. 

 fifteen days old, beneath the vulva were observed two protulierances exactly like the 

 testicles of the male, and which, on examination after death, j>P>ved t^) be the ovarieo. 

 The other organs of generation were normal. The same Sow which produced them, had, 

 in a previous litter, brought forth two females with the ovaries similarly misplaced. 



4 



