Rectal Palpation 97 



ing of the crater when the ovisac ruptured. The two ovaries 

 are rarely symmetrical ; the left is usually the smaller — not 

 rarely, minute, — no larger than a small pea. From such a 

 minimum, the healthy ovary may be of any size, up to two, 

 or even three inches in some large cattle. 



The corpus luteum modifies greatly the gross volume of the 

 ovary. In the very small ovary, the corpus luteum, fully de- 

 veloped, may increase the volume of the organ ten- to twenty- 

 fold, while the development of a seven-eighths inch corpus 

 luteum in an ovary of two inches, though actually adding the 

 same volume, does not cause the great comparative increase 

 in size. 



The healthy corpus luteum of the non-pregnant heifer or 

 cow retains its maximum volume until about the sixteenth to 

 eighteenth day after ovulation, when it atrophies rapidly for 

 two or three days, and at twenty to twenty-two days, when 

 it has decreased to one-fourth or three-eighths of an inch in 

 diameter, estrum and ovulation recur. After the corpus 

 luteum has formed as a solid mass, physiologically it remains 

 solid throughout its history. It is solid, firm, and somewhat 

 elastic to the touch. 



The corpus luteum of pregnancy does not differ (except in 

 color, which is of no concern here) from the corpus luteum 

 of estrum in its general characters, but in duration it phys- 

 iologically continues unchanged throughout pregnancy and 

 for thirty to sixty days thereafter, when it atrophies and 

 estrum and ovulation recur. Pathologically, the corpus 

 luteum may be grossly enlarged to even two or three inches 

 in diameter, may undergo cystic degeneration, and other- 

 wise depart from the normal volume, consistence, and char- 

 acter. It may undergo rapid degeneration, with abnormally 

 short intervals between estrual periods, may atrophy dur- 

 ing pregnancy and cause ovulation and estrum, may shift its 

 position and sink deeply into the body of the gland, and may 

 persist at full size for month after month, even to years, in- 

 hibiting estrum and ovulation. The ovary is subject to such 

 a wide variety of pathologic changes that the veterinarian 

 needs to study it carefully and abundantly both in the abat- 



7 



