120 Diseases of the Ge?iital Orga?is 



4. The Corpus Luteum of Pregnancy 

 (See Fig. 26) 



Physiologically, a corpus luteum develops after each es- 

 trum, and is of the same form, size, and consistency, whether 

 the animal be pregnant or not. In sterility, however, the 

 corpus luteum is one of the most common sufferers from 

 pathologic changes. The bovine corpus luteum of preg- 

 nancy is normally five-eighths to three-quarters of an inch 

 in diameter, somewhat oval in form, usually even in con- 

 tour, and firm in consistency. Forming, as it does, within 

 the crater left behind when the ovisac ruptures, it is at first 

 naked. That is, it is not covered by the tunic of the ovary 

 and it protrudes somewhat beyond the surface of the gland. 

 If the animal conceives, the tunic of the ovary soon draws 

 over the surface of the yellow body and leaves it smooth 

 and firm. The wound is healed. Sometimes a considerable 

 projection remains, even though the tunic has drawn over 

 the yellow body. In sterility, however, the wound in the 

 ovisac frequently fails to heal and the yellow body remains 

 for a long period of time protruding and naked. The pro- 

 truding dome feels soft upon palpation, like the exuberant 

 granulation of an unhealthy ulcer. The corpus luteum of 

 sterility frequently undergoes cystic degeneration in its 

 center. It becomes soft and more or less fluctuant, accord- 

 ing to the degree of degeneration. Finally, as the degenera- 

 tion extends, the lutein tissue disappears and a cyst remains. 

 When one can recognize these conditions in the ovary, he 

 can with very rare exceptions rest assured that pregnancy 

 has not occurred through fertilization of the ovum which 

 was discharged from the ovisac in which the diseased yellow 

 body develops. He must not be deceived, however, because 

 of the presence of a cyst or cysts in an ovary. The typical 

 corpus luteum of pregnancy almost always exists in a preg- 

 nant animal, but cysts may co-exist. Accordingly, while the 

 absence of a corpus luteum of a normal type is fairly con- 

 clusive evidence that the animal is not pregnant, the co- 

 existence of a large cyst in the same or other ovary is not 

 final proof, though it is strong evidence that the animal is 



