Abdominal Cavity and Uterus. 323 



No doubt, as I then suggested, the multitude of minute 

 ovisacs thus found in the infundibulum are what from their 

 position I termed parasitic, these having been involved in 

 the rupture of a Graafian follicle, and thus expelled. Lying, 

 however, as these do, between a larger ovisac and its vascular 

 covering, the escape of the parasitic ovisacs implies the ex* 

 pulsion of the larger one. And it is very possible that it 

 was this larger ovisac with its ovum that I have just men- 

 tioned as having been represented by a drawing.* 



Whether such was the case, however, it matters not. All 

 that I wish to shew from the said observation is simply this : 

 That ovisacs in large numbers are found outside the ovary, 

 and therefore that ovisacs are expelled from that organ. 



But farther, I have reason to believe that in most instances 

 the Hogs, in which are frequently found such ruptured Graa- 

 fian follicles, have had no connection with the male. And 

 lastly, from what I have since noticed in other Mammalia, 

 and especially in the Rabbit, I am satisfied that the following 

 is common to this class of animals, viz. — In the rutting season 

 when there has been no connection with the male, the ovum 

 does not escape from its ovisac ; for the ovisac itself is ex- 

 pelled from the ovary with the unfecundated ovum contained 

 in it. 



Of what I had thus seen to happen in Mammalia on the 

 expulsion of an ovum from the ovary in the rutting season, 

 when there had been no connection with the male, I was re- 

 minded by Keber's facts. And the conviction arose, that 

 the vesicles with a rotating body — certainly not ova — are 

 ovisacs. In favour of such an opinion was the fibrous struc- 

 ture of their membrane, t and their usually large size. I 

 have already published this view, J and have since received a 



* Phil. Trans., 1839, PL V., fig. 102. 



t In the fibrous structure of the membrane of the vesicles containing a rotat- 

 ing body, Keber foresaw an objection likely to be raised against his view that 

 they are ova ; the vitellary membrane (zona pellucida) never becoming fibrous. 

 This objection has been met by my opinion, that they are not ova but ovisacs. 

 For drawings which I gave in 1841 of young ovisacs present, in the nucleolated 

 nuclei of which their membrane is at first composed, the elements of future fibre. 

 (Phil. Trans., 1841, PI. XXV., figs. 164 to 173.) 



t In the last number of this Journal. 



