38 OBSTETPJCAL ANATOMY. 



mucus (in woman this mucus is acid, while that of the uterus is 

 alkaHne), and is disposed (in the Mare) in longitudinal rugie, which 

 are more conspicuous after several births. These rugae no doubt favour 

 the dilation of the canal during coitus or the passage of the foetus ; a 

 transverse ridge, already described as existing on the lower face of the 

 canal, covers the meatus. This membrane is continuous with that 

 of the vulva, and anteriorly, at the cul-de-sac, it is reflected over the 

 cervix of the uterus, which projects, like a cauliflower in shape, into 

 the cavity. It is provided with papillae, and covered with pavement 

 epithelium. It usually has a pale pink hue, but at the period of 

 oestrum its colour becomes heightened to a bright red, and its secretion 

 is considerably increased. 



Externally, the vagina is invested by a muscular coat, which is 

 enveloped by an abundant layer of connective tissue, and traversed by 

 a large number of bloodvessels ; in front, how^ever, this tunic is invested 

 in peritoneal membrane, which is applied in a circular manner around 

 it, to pass over the uterus. 



The vagina is supplied with blood by the internal pudic artery ; its 

 veins are disposed as an encircling plexus, and terminate in the satellite 

 trunk of the artery. The vagina serves for copulation and the passage 

 of the foetus. At the periods of oestrum and parturition, the mucous 

 secretion is more active than at other times. In youth it is contracted ; 

 after copulation its dimensions are increased, and these are greatest 

 during parturition. In old age it is much diminished; in the third or 

 fourth months of gestation in the larger animals, it becomes elongated 

 from displacement of the uterus, which is carried farther forward into 

 the abdominal cavity ; towards the termination of this process its 

 length diminishes as the uterus acquires increased volume, and to 

 such an extent does this occur, that at the commencement of parturi- 

 tion, if the foetus is large, and especially if there be two foetuses, the 

 posterior wall of that receptacle, pushed back into the pelvis, nearly or 

 entirely effaces the cavity of the vagina, and even in some instances 

 thrusts it between the labia of the vulva or beyond. 



The vagina has been found partially divided into two canals by a 

 niedian, though incomplete, vertical septum, which was so short that 

 it could not be said to form a double vagina. 



Differences. 

 Coiv, Sheep, and Goat. 

 In the Cow the canal is longer and wider than in the Mare ; the 

 mucous membrane of the vagina is thicker, is disposed in transverse 

 rugae as in the human species, and at each side of the passage for a 

 certain distance, between the mucous and muscular layers, there exists 

 a mucous canal that opens into the vulvar cavity, in front of, and at 

 the side of the meatus urinarius. 



The uses of these canals, which are not present in the Sheep or Goat, 

 and rarely in the Mare, and which are usually known as the " canals of 

 Gaertner," are unknown. They pass backwards into the broad ligaments 

 of the uterus, and terminate in a cul-dc-sac. They probably have some 

 function during fa^tal life. 



Puj. 



In the Pig these canals are present ; the folds of mucous membrane 

 are longitudinal, and gradually subside towards the line of separation 



