On Abortion in Cows. 



69 



The vagina h is a large passao^e lying behind the uterus, under 

 the rectum, and behind and above the bladder ; it is the commu- 

 nication between the uterus, orifice of the bladder, and external 

 organs of generation. In the virgin it exceeds the uterus in size, 

 and, like that organ, is lined by a moist membrane. 



By the time that the young female is fit for the propagation of 

 her species, the ova, or cells in the ovaries, have also attained 

 that degree of development which is necessary to ensure fruitful 

 connection with the male. As they ripen they gradually approach 

 the outer surface of the ovary (see d, fig. 3, and e, fig. 5) : this 'is 

 a periodical process, and takes place during each season of heat, 

 or oestrum, at intervals of three weeks or so m healthy cows in 

 good condition. At this time the broad trumpet-shaped ends of 

 the fallopian tubes c, fig. 5, are closely applied over that part of 

 the ovary which contains the ripened ovum. The ovum on 

 reaching this situation causes the wall of the ovary to give way,. 

 e and f, fig. 5, and, passing into the expanded entrance of the 

 fallopian tube, is carried to the uterus. Asa result of copulation, 

 the male seed passes from the uterus along the tube, and comes 

 in vivifying contact with the ovum on its escape from the ovary^ 

 After this union or contact between the active reproductive prin- 

 ciples of the sexes, certain further changes take place, one of 

 which is, that the ovum, in passing along the tube to the uterus, 

 becomes invested externally by a rougli covering, which after- 

 wards forms a foetal membrane, and is subservient to important 

 uses. When the ovum reaches the uterus it is subjected to 

 further and very complicated changes. It loses the simple cel- 

 lular character, and in a few weeks presents an indistinct or 

 embryonic resemblance to the future animal. During the transit 

 of the ovum ahmg the fallopian tubes the interior of the uterus 

 undergoes changes preparatory for its reception : a membrane 

 called the decidua is formed, and becomes the medium of con- 

 nection and nutrition between the uterus and its contents. 



During the time that development of the foetus is going on 

 there is a gradual formation, and increase in capacity and strength, 

 of certain membranes by which it is surrounded. The most 

 important of these are termed the amnion, allantois, and chorion. 

 The amnion, fig. 6, 11, 11, 11, lies nearest to the foetus; it is a 

 soft, remarkably pliable, transparent sac, and contains a great 

 quantity of thick gelatinous fluid, called the liquor amnii, in 

 which the foetus floats, securely protected, as in a hydrostatic bed. 

 The amnion is proKmged over the vessels of the navel string, 

 9, fig. 6, and becomes attached to the margins of the opening 

 through which these vessels enter the body of the foetus. The 

 allantois, 8 8, is a kind of membranous bag situated between the 

 chorion and amnion. Amongst other uses, it serves the purpose 



