OESTRUM AND CONCEPTION 6 



flow of bloody mucus from the vulva ; this is known as " still 

 bulling." The beginning of oestrum is indistinct, reaches its 

 height in a cow in twenty-four hours, and then declines. At 

 the outset of oestrum the female does not take the bull. The 

 period of oestrum in the cow is twenty-four to thirty-six hours. 

 In case conception does not take place, it repeats itself every 

 three weeks. AYhenever conception takes place, it is, as a 

 rule, wanting during pregnancy. Four weeks after parturition 

 oestrum appears. Although no definite time exists for concep- 

 tion, it seems to occur more readily in spring. During 

 oestrum weak uterine contractions occur, which open the cervix 

 sufficiently to permit the introduction of a finger. As a conse- 

 quence of these contractions a mummified foetus may be ex- 

 pelled. Some cases are on record where a cow was covered 

 during the period of oestrum. The following day a dried 

 foetus was expelled ; nevertheless the animal remained preg- 

 nant (Franck). As previously stated, oestrum represents a 

 series of symptoms prising from the ovaries and of great 

 importance to us. 



At an early age — in the foetal ovary— the Graafian follicle 

 has been proved to exist. During puberty a decided hyper- 

 semia of the ovary occurs, and one or more follicle enlarge and 

 project above the ovary, giving the latter the appearance of 

 a mulberry, and at this moment "the Graafian follicle is 

 matured." The Graafian follicle bursts, and the ovum is 

 received by the fibriated extremity of the oviduct. The 

 pavilion of the tube containing non-striated muscular tissue 

 grasps the ovary with its fimbriae. 



The ovum is a cell with a diameter of T V to -fa mm., and 

 consists of a rather thick and transparent membrane (vitelline 

 membrane, zona pellucida), and its contents, the yolk or 

 vitellus, made up of a number of granules joined by a viscid 

 fluid. The vitellus contains the germinal vesicle and the 

 germinal spot. Studies within the last few years show that 

 the egg cell undergoes a number of microscopical changes 

 before fecundation can take place. 



Corpus Luteum.— When the Graafian follicle ruptures and 



