PERITONEAL RELATIONS OF THE MAMMALIAN OVARY. 41 



of the sac, the ovary is on the upper border, and projects down into 

 the sac. The Fallopian tube forms a distinct widely open curve 

 in the wall of the sac. Examples — Coelogenys paca, Cynocephalus 

 parcarius, elephant, &c. 



3. A class in which the growth of the Fallopian tube and broad 

 ligament takes place as in the second class, but the edge of the 

 broad ligament posterior to the ovary has become adherent to the 

 free edge of the secondary fold caused by the ovarian ligament ; 

 consequently the orifice of the sac, which is directed inward and 

 upward towards the spine, is a narrow slit, equalling, or but slightly 

 exceeding, in length the long diameter of the ovary. Examples — 

 guinea pig, bitch, porcupine. 



4. A class the sac of which is formed as in the third class, but, 

 further, the lower edge of the orifice has become adherent to the 

 inner face of the ovary along the white line, except at the point 

 posteriorly where a minute orifice is left, from which one or two 

 fimbria project. The ovary and the greater portion of the infundi- 

 bulum are enclosed in the sac, and are not visible until the sac wall 

 has been opened. Examples — racoon and badger. 



In both the examples of the latter class it must be noted that the 

 ovarian ligament is very short, almost absent. The ovary lies close 

 to the tip of the uterine cornu, the Fallopian tube is short, and the 

 sac wall not flaccid, but closely applied to the surface of the ovary. 



Numerous examples of these different types, or forms, of ovarian 

 sac have been described and figured by previous observers. There 

 is, however, a still further modification of the relations between the 

 cavity of the ovarian sac and the general cavity of the peritoneum, 

 and one of peculiar interest, since it results in the entire separation 

 of these cavities from each other, and therefore in the formation of 

 a distinct and complete ovarian sac. This condition I have met with 

 in animals so common as the rat and mouse • still, so far as I am 

 aware, it has not yet been described, and I have therefore the less 

 hesitation in referring to it in detail. 



While examining the reproductive organs of the white variety of 

 the common house mouse {Mus musculus), and also those of the white 

 variety of the common brown rat {Mus decumanus), I found that on 

 superficial observation the ovaries appeared to lio outside the peri- 

 toneum ; but when the layer of peritoneum covering the surface of 



