CHANGES IN THE OVARY 141 



ovum was shot into the open fimbriae in the act of ejaculation. 

 The motion of the cilia, which line the fimbriated end as well as 

 the interior of the tube, no doubt serve to set up a current 

 which assists in directing the ova. Gerhardt,^ who has paid 

 some attention to the question, concludes that in Man and many 

 other Primates a number of factors co-operate to secure the 

 entry of the discharged ovum into the tube. These factors 

 include the erectibihty of the fimbriae, the muscular movements 

 of the same, the ciliary currents on the fimbriae and tube, and 

 the configuration of the ovarian surface. In other orders of 

 Mammals the process is brought about in various ways. In 

 Monotremes, Marsupials, and Cetaceans the entrance to the tube 

 is relatively large as compared with the size of the ovary. In 

 certain other animals a portion of the peritoneum is used as a 

 common envelope for the ovary and the end of the tube. Thus 

 in the dog and ferret the ovary is enclosed in a sac communicating 

 with the cavity of the tube, so that the discharged ova can 

 scarcely fail to effect an entrance into the uterus. There can 

 be Uttle doubt, however, that in the majority of animals ciliary 

 movement plays an important part in directing the course of 

 the expelled ova. 



Nussbaum ^ has described the eggs of the frog as being 

 carried into the mouths of the oviducts by the motion of the 

 cilia of the coelomic epithelium. These ciha are said to drive 

 in a forward direction any small bodies lying free in the coelom. 

 Harper ^ states that in the pigeon the egg is clasped by the 

 oviduct, which at this time displays active peristaltic contrac- 

 tions, 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 bicornuate uterus becoming pregnant 

 in the uterine horn on the side opposite to that on which the 

 ovary had discharged (as indicated by the presence of a newly 



' Gerhardt, " Studien iiber den Gesohleohtsapparat der Weiblichen Sauge- 

 thiere : I. Die Ueberleitung des Eies io die Tuben," Jenaische Zeitschr., 

 vol. xxxix., 1905. 



' Nussbaum, "Zur Meohanik der Eiablage bei Rana fusca," Arch. f. Mikr. 

 Anat., vol. xlvi., 1895. 



' Harper, loc. cit. 



