Extra- Uterine Pregnayicy 415 



and cross ov^er to the opposite ovary. It has also been experi- 

 mentally shown that, in rare cases, an ovum which has escaped 

 from one ovary, but failed to enter the corresponding oviduct, 

 may pass across to the other ovary and enter its Fallopian tube. 

 An egg which has emanated from one ovary may become fertil- 

 ized, pass through the corresponding oviduct and cornu to the 

 uterine body and thence upward into the opposite cornu, to be- 

 come attached and develop into an embryo. The evidence of 

 such occurrence is found in the fact that a fetus sometimes de- 

 velops in one uterine cornu, while the yellow body from which 

 the ovum evidently emanated is located in the opposite ovary. 



Polyspermia. 

 It is believed by some authors that an ovum may be over- 

 fertilized, that is, instead of one spermatozoon penetrating an 

 ovum, two or more gain admission to it, in which case the devel- 

 opment may be abnormal and lead to the formation of some of 

 the double or triple monstrosities. 



Extra-Uterine Pregnancy. 



Extra-uterine pregnancy is the existence, for a greater or less 

 period of time, of a living ovum outside the uterine cavity, 

 within the abdomen. The precise nature of most cases of alleged 

 extra-uterine pregnancy in animals has not been definitely 

 ascertained and, before arriving at any final conclusion as to their 

 nature, the subject needs much investigation. Not infrequently 

 fetuses are found outside the uterus in the abdominal cavities 

 of animals, but it has not been clearly shown how they attained 

 this position. Many records are given of the finding of such 

 fetu-ses in the peritoneal cavity, but their anatomical relations 

 are not recorded. 



Several forms of extra-uterine pregnancy occur : 

 I. Ovarian pregnancy has been recorded and verified. In 

 these cases it appears that the ovisac ruptures, but the ovum does 

 not escape from it and spermatozoa, pa.ssing up through 

 the oviduct and pavilion of the tube, reach the ovum and bring 

 about its fertilization. The ovum may then undergo a develop- 

 ment analogous to that observed in the uterus, either enclosed 

 within the ovary or attached to it by the fetal membranes. The 

 records of ovarian pregnancy are exceedingly rare, and as a rule 



