358 THE ANATOMY OF THE HORSE. 



in the previous description of parts, it may be said. to begin on the 

 surface of the body at the vertical slit already described, and to 

 terminate in front by joining the tube of the vagina. In the 

 adult animal there is little to mark the line of separation between the 

 two passages, but in the young animal a membranous septum — the 

 hymen — stretches between the two. This is occasionally seen also in 

 the adult mare, and more frequently a few warty projections — the 

 caninculm myrtiformes — which are the shrunken remains of the hymen, 

 stud the line of junction ; but very often the canal of the vulva passes 

 withotit interruption into that of the vagina. The vulva is lined by a 

 mucous membrane of a rosy, vascular tint. It possesses numerous 

 mucous follicles ; and its free surface is formed by a stratified sqxiamous 

 epithelium, which, towards the external opening, is often pigmented in 

 spots. 



The Meatus Urinaeius. The urethra opens on the middle line of 

 the floor of the vulva immediately behind its point of continuity with 

 the vagina. The opening is surmounted by a large mucous fold — 

 the valve of the meatus winarius. This valve has its free edge 

 directed backwards, and it serves to direct the flow of urine towards 

 the exterior. Its presence must be remembered in passing the 

 female catheter, the point of which should be made to press on the floor 

 of the vulva as it is directed onwards. The meatus is of large size 

 when compared with the same orifice in the male, since it readily admits 

 two fingers. 



Directions. — Reverse the natural position of parts, laying the uterus, 

 vagina, and vulva with their upper surfaces downwards, and open the 

 bladder by a mesial incision on its lower (in the natural position) face. 

 For an account of the structure of the bladder turn to page 347. 



The Urethba of the female is very much shorter, but considerably 

 wider, than the corresponding tube of the male. Beginning as a funnel- 

 like prolongation of the neck of the bladder, it passes backwards on the 

 middle line of the lower face of the vagina, in whose wall it is partially 

 imbedded ; and after a coui-se of two or three inches it perforates the 

 lower wall of the vulva, and opens by the meatus already described. 

 The calibre of the tube is in correspondence with the large size of the 

 meatus ; and with slight stretching it will accommodate three fingers. 

 The wall of the urethra is composed of connective-tissue, and non- 

 striped muscular fibres circularly disposed; and it is lined internally 

 by a longitudinally folded mucous membrane with a stratified squamous 

 epithelium. 



Structuke and Interior op the Vagina. The tube of the vagina 

 is about nine or ten inches in length. Posteriorly it joins the vulva, 

 and anteriorly it embraces the cerv'ix uteri. The connection between 

 the cavities of the vagina and uterus is, thus, not by simple continuity. 



