I 3 6 THE PHYSIOLOGY OF REPRODUCTION 



tin- peritoneum is used as a common envelope for the ovary and the 

 end of the tulf. Thus in the dog and ferret the ovary is enclosed 

 in a sac communicating with the cavity of the tube, so that the 



barged ova can scarcely fail to effect an entrance into the uterus. 

 There can be little douU, however, that in the majority of animals 

 ciliary movement plays an important part in directing the course of 

 the expelled ova. 



Nussliaum 1 has described the eggs of the frog as being carried 

 into the mouths of the oviducts by the motion of the cilia of the 

 ccelomic epithelium. These cilia are said to drive in a forward 

 direction any small bodies lying free in the ccelom. Harper 2 states 

 that in the pigeon the egg is clasped by the oviduct, which at this 

 time displays active peristaltic contractions, as if in the act of 

 swallowing the egg. 



There is evidence, however, that ova which are discharged from 

 one ovary do not always pass into the oviduct on the corresponding 

 side. For example, instances have been known of animals with a 

 liicornnate uterus becoming pregnant in the uterine horn on the 

 side opposite to that on which the ovary had discharged (as indicated 

 l>y the presence of a newly formed corpus luteum). Moreover, it 

 has been recorded that animals from which one ovary had been 

 removed have become pregnant in the uterine horn of the other 

 side, an observation which indicates that the ova which are discharged 

 from one ovary may travel across the peritoneal cavity and enter 

 the Fallopian tube whi'-h \v;is connected with the other ovary. 3 



It has been stated that in certain abnormal cases an ovum which 

 escapes altogether into the peritoneal cavity may yet become fertilised, 

 bringing about a condition of abdominal pregnancy. There can be 

 little doubt, however, that abdominal pregnancy is nearly always 

 secondary to tubal pregnancy, and that primary ectopic pregnancy 

 i> <-.vfediiio;ly rare. According to Loeb 4 the uterine mucosa is the 

 only form of tissue which is able to produce a decidua in the guinea- 

 j>i'_ r . and whil'- an ovum in the body cavity may undergo the early 

 stages of development, lack of the proper response on the part of the 

 h< t -tissue (lack of decidual reaction) renders development of the 

 later stages of extra-uterine growth impossible Blair Bell, 5 however, 



1 Nussbauin. "/in- Merhanik <lvr KiaMage l>ei A'-///'/ /<>.<(" Arch. f. Mil.r. 

 .I. xlvi., iw.". * Harper, /(: ,-it. 



Hammond, "On some Factors Controlling Fertility in Domestic 

 Animal.H," ,/<ir. Agri'. >'///, vol. vi., 11)14 (for rabliits and pigs), and Corner, 

 "The (Virpns l.uteum of Pregnam-y as it is in Swine," ('uiitrilmtidnx to 

 k'inl'r>/<>/<*/</, \ol. ii.. Carnegie Institute I'nh., 1 !)!;". Intrrnal migration of ova 

 fn>m one ut<-rin- horn to another haa been shown to be not uncommon. 



4 Ijoeb (L.), "The Experimental Production of an 'Early Stage of Extrauterine 

 Pregnancy.' Pne. .w. /-:.,- r . /!,,,/. .I/,-,/., vol. \L lit) 4. 



Blair IU-11. " I'rimarv AlMlominal Pregnancy in a Rabbit," Proc. lion. Soc. 

 I'.tll. 



