142 THE PHYSIOLOGY OF REPRODUCTION 



formed corpus luteum). Moreover, it has been recorded that 

 animals from which one ovary had been removed have become 

 pregnant in both horns of the uterus, an observation which 

 clearly shows that the ova which are discharged from one ovary 

 may travel across the peritoneal cavity and enter into the 

 Fallopian tube on the other side of the body. 



In certain abnormal cases the ovum escapes altogether into 

 the peritoneal cavity, and never finds its way into either ovi- 

 duct. If the ovum becomes fertihsed, as sometimes happens, 

 the condition known as ectopic or extra-uterine gestation may 

 result ; that is to say, the embryo which is formed may become 

 attached to some part of the wall of the body cavity and there 

 undergo development. Ectopic or extra-uterine pregnancy has 

 been known to occur in the domestic animals as well as in the 

 human subject.* Thus Gofton^ has recently described a case 

 of a cat which was pregnant with six kittens, one in the normal 

 position in the uterus, and the other five in -the abdominal 

 cavity. The fcetal envelopes of the abdominal embryos were- 

 attached by a sort of placenta to the parietal peritoneum -and 

 to the omentum, and one had also an extensive attachment 

 to the fundus of the stomach. All the embryos were well 

 developed and apparently nonnal. Moreover, Dr. Blair Bell 

 has informed me of a case of primary abdominal pregnancy in a 

 rabbit owned by him. There were four well-developed foetuses. 



The Formation of the Corpus Luteum 



After the discharge of the ovum from the ovary the ruptured 

 Graafian follicle undergoes a series of changes which result in 

 the formation of the structure known as the corpus luteum. 



The fully formed corpus luteum consists of large cells con- 

 taining a yellow pigment, the luteal cells, separated from one 

 another by an anastomosis of connective tissue which is seen 

 to branch inwards from the surrounding ovarian stroma, and 



1 See the text-books on Midwifery, and for further details, The Journal of 

 Obstetrics and Gynmeology, vol. x., December 1906, which number is entirely 

 devoted to the subject of extra-uterine pregnancy. Ovarian pregnancies, in 

 which the spermatozoa have entered newly ruptured follicles, are also known. 



* Gofton, "Ectopic Gestation in a Cat," Royal Dick CoU. Mag., vol. 

 i., 1906. 



