422 Diseases of the Genital Orgaris 



be normal, the health of the patient is apparently perfect, 

 and there is present in one of the ovaries a typical corpus 

 luteum of ordinary size, form, and consistency. Under 

 these conditions, persistent corpus luteum is diagnosed. The 

 diagnosis may be subject to question. It is quite possible 

 that in many cases estrum has been overlooked. Since some 

 cattle are not demonstrative and some attendants are not 

 very alert in recognizing estrum, it is not improbable that 

 many cases diagnosed as persistent corpus luteum are really 

 instances of failure upon the part of the attendant to ob- 

 serve estrum. However frequent error may be, the condi- 

 tion does occur and should be promptly recognized by the 

 veterinarian. I have observed cows where every opportu- 

 nity was given for them to exhibit symptoms of estrum and 

 where they had shown no such signs over a period of six 

 months or more. Upon examination, the entire genital sys- 

 tem is found to be normal, including an apparently normal 

 corpus luteum in one of the ovaries. The general health of 

 the animal is beyond criticism, and no apparent reason ex- 

 ists for failure of ovulation and estrum. Under these condi- 

 tions the dislodgment of the corpus luteum causes the 

 prompt appearance of estrum, and as a general rule the ani- 

 mal conceives readily. The long inhibition of estrum has 

 apparently served as a definite and valuable period of rest, 

 so that, when the barrier is overcome and the genital or- 

 gans function, conception is prompt. 



9. The Central or Embedded Corpus Luteum. The 

 Corpus Luteum of Pyometra and Fetal Retention 



When an ovisac approaches maturity, it pushes its way, in 

 the cow, toward the convex, free surface of the ovary, to 

 protrude eventually beyond the general ovarian surface. 

 It then ruptures and the corpus luteum which forms in its 

 crater, when grown, also projects above the ovarian level. 

 Such projection persists throughout the physiologic career 

 of the body, until it atrophies preparatory to a new ovula- 

 tion, when it may (or may not) sink more deeply into the 

 gland as it gradually disappears. 



