CHANGES IN THE OVARY 137 



has described a case of primary abdominal pregnancy in the rabbit 

 where four foetuses were found attached to the gastro-colic omentum. 

 Gofton * has 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 foetal 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. According to Webster 2 ectopic pregnancy 

 always originates as tubal pregnancy, the tube subsequently under- 

 going rupture. Huffman 3 explains extra-uterine pregnancy as due 

 to an embedding in anomalous, but specialised tissues, arising from 

 a rudimentary second uterus or other accessory reproductive organs. 

 Tubal pregnancy is generally believed to be due to inflammatory 

 trouble which interferes in some way with the downward movement 

 of the fertilised ovum, 4 but Loeb and Hunter 5 state that in the 

 guinea-pig it is impossible to bring about tubal pregnancy through 

 a mere retention of the ovum in the Fallopian tube. 



Ovarian pregnancy is very rare, although well authenticated. 



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 containing 

 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 to form a central plug in 

 which there are no luteal cells. This connective tissue contains 

 numerous blood-vessels, so that the fully developed corpus luteum is 

 a highly vascular structure. 



Three hypotheses have been put forward regarding the manner 

 of formation of the corpus luteum. That of Paterson, 6 who supposed 

 it to be derived from the blood coagulum left in the cavity of the 

 Graafian follicle after its discharge, gained few or no adherents. The 



1 Gofton, "Ectopic Gestation in a Cat," Royal Dick Coll. Mag., vol. i., 

 1906. 



2 Webster, Ectopic Pregnancy, New York, 1895. 



3 Huffman, "A Theory of the Cause of Ectopic Pregnancy," Jour. Amer. 

 Med. Assoc., vol. Ixi., 1913. 



4 Mall, On the Fate of the Human Embryo in Tubal Pregnancy, Carnegie 

 Institute (Washington) Pub. No. 221, Washington, 1915. 



5 Loeb and Hunter, " Experiments concerning Extrauterine Pregnancy," 

 Pennsylvania Med. Bull., 1908. For further references the above papers may 

 be consulted. 



6 Paterson, "Observations on Corpora Lutea," Edinburgh Med. and Surg. 

 Jour., 1840. 



