CESTEUM AND CONCEPTION 3 



flow of bloody mucus from the Tulva ; 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. Whenever 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 fcetns 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 -^ to -^ 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 



