56 Diseases of the Genital Organs 



suitable location in the uterus, and become implanted there 

 before it can advantageously receive ample nutriment for 

 needed growth and development. The migration through 

 the oviduct must occur with sufficient celerity that the ovum 

 shall enter the uterine cavity prior to any noteworthy 

 growth in volume for the reason that the lumen of the tube 

 is so small that important increase in the size of the egg 

 would imperil its passage. It is probably owing to patho- 

 logic decrease in its lumen that the ovum occasionally 

 lodges in the oviduct of woman (tubal pregnancy), de- 

 stroying the life of the embryo and greatly imperilling 

 the life of the mother. The migration of the ovum, 

 unlike that of the spermatozoa, is passive and is brought 

 about by the action of the cilia of the tubal epithelium which 

 wave toward the uterus, and probably by muscular action 

 in the walls of the oviduct. The time required in domestic 

 animals is not known but in the cow it is probably eight to 

 fifteen days. 



11. The Corpus Luteum of Pregnancy 



The formation of the corpus luteum of pregnancy is fun- 

 damentally like that of estrum as described above. Its 

 source of origin, its method of growth and its ultimate vol- 

 ume is the same. It presents two notable characters which 

 serve to distinguish it. 



The color of the corpus luteum of pregnancy in the cow 

 is regularly of a bright lemon color, in contrast with the 

 chestnut or muscle-colored structure of estrum. The color 

 distinction is not universally present. Amongst approxi- 

 mately 2000 pregnant cows and heifers, I have observed two 

 corpora nigra, or black bodies, one normal in size, the other 

 about double the normal volume. The rule of chestnut color 

 for the corpus luteum of estrum and lemon or orange color 

 for the corpus luteum of pregnancy appears at times to be 

 reversed. Some have claimed that the corpus luteum of 

 estrum is often lemon or orange-colored but I believe most 

 of these reports are referable to error. That is, observers 

 not familiar with their ground see in the abattoir an empty 



