DISEASES OP HORSES AND CATTLE. 301 



womb. The inner membrane of the womb, by the 

 time that the impregnated ovum reaches it, be- 

 comes thickened and velvety looking, and full of 

 small blood vessels; and although the blood ves- 

 sels of the one have no direct communication with 

 the other, but being very vascular and in close con- 

 tact, the blood of the mother, loaded with matters 

 necessary for the growth and vitality of the young 

 creature, is constantly going on between them. In 

 the cow the points of connection between the 

 mother and foetus are the cotyledons, already men- 

 tioned on the inner lining of the womb, and a num- 

 ber corresponding on the outside of the chorion of 

 the foetus. The placenta or afterbirth is com- 

 posed of three membranes. First: The chorion, 

 the one already described. Second: The amnion, 

 called the water bag. Third: The allantoid. The 

 amnion contains a fluid in which the young crea- 

 ture floats, and the escape of this fluid is one of the 

 earliest signs of parturition. The allantoid mem- 

 brane is situated between the chorion and amnion 

 and acts as a receptacle for the urine of the foetus, 

 being connected by a tube called the urachus to 

 the bladder. This tube at the time of birth is rup- 

 tured and shrivels up and the urine passes by the 

 proper channel. In some cases, especially in the 

 foal, the urine passes both ways on account of this 

 tube not shriveling up. The umbilical cord or na- 

 vel string is formed by this urachus and the blood 

 vessels which pass from the chorion to the foetus. 

 In the act of parturition this cord is usually rup- 

 tured. These membranes connected are what 



