112 Diseases of the Genital Organs 



or field, as is commonly done in winter for only a brief in- 

 terval, a cow may pass through her active estrual period' 

 during the interval between two periods in the paddock. 

 Not infrequently such unrecognized estrual periods result 

 in expensive delay in breeding. 



The chief evidences of estrum revealed upon physical ex- 

 amination are : 



(1) The vagina contains much thin, lubricant, clear mu- 

 cus. In metritis, cervicitis, and vaginitis the mucus may 

 contain floccules of muco-pus. The flow of the mucus of es- 

 trum appears in the vagina twenty-four hours or more prior 

 to the establishment of sexual desire and terminates about 

 twenty-four hours after the cessation of estrum. If fertiliza- 

 tion fails, the discharge of estrual mucus is displaced by the 

 menstrual flow. 



(2) The cervix is relaxed and the canal more dilated and 

 dilatable than in the inter-estrual period of rest. 



(3) The uterus is engorged. Prior to the full develop- 

 ment of estrum, the uterus may be normal to the touch at 

 first, but under palpation becomes engorged or erected. 

 When estrum is at its height, the engorgement is constant. 

 The diameter of the engorged uterus of estrum is increased 

 about one-half, is much firmer than during the inter-estrual 

 pause, and is smooth, even, and very firm. It is about the 

 same size as the pregnant uterus at thirty to forty days, but 

 is distinguishable by its firm, engorged character, in con- 

 trast with the fluctuant, tense uterus of pregnancy. It is 

 less hard, and smaller than the uterus of chronic sclerotic 

 metritis with destruction of the uterine mucosa. 



(4) The corpus luteum of the preceding estrum is atro- 

 phied to about one-half its ordinary diameter, or about three- 

 eighths of an inch. 



(5) There is present, generally upon the opposite ovary, 

 a mature ovisac, a thin-walled cyst one-half inch or a trifle 

 more in diameter. (See Figs. 22-25.) 



If it is desired to breed the animal during the existing es- 

 trum, the examiner needs to be very cautious in palpating 

 the ripe ovisac since under very slight pressure it ruptures, 



