880 THE GENEEATIVE APPABATUS. 



cylindrical, ttterine, or utricular glands are closely clustered together, 

 sometimes bifurcated, often twisted in a spiral fashion, and terminating in a 

 cul-de-sac in the substance of the membrane. In structure they resemble 

 other mucous glands, consisting of a membrana propria, an epithelium of 

 spheroidal cells at the bottom of the tube, and of columnar cells in its duct. 

 During gestation they are much enlarged, and receive the cotyledonal 

 processes of the placenta. At the period of oestrum, the glandular secretion 

 of the uterus is more active than at other times.) 



Vessels^Nerves. — The blood brought to the uterus by the uterine- and 

 utero-ovarian arteries, is conveyed from it by veins corresponding to the 

 latter. In animals which have been pregnant several times, the vessels are 

 remarkable for their enormous volume and their tortuousness. (The 

 arteries freely anastomose ; they ramify through the muscular and mucous 

 tunics, constituting coarse and fine networks which ultimately end in the 

 veins. These are very large and have no valves ; the plexuses they form 

 are considerable.) 



The lymphatics that pass from the uterus are as remarkable for their 

 number as their dimensions ; they reach the sublumbar region. 



The nerves supplying the organ come from the small mesenteric and 

 pelvic plexuses. (In the uterus there are several important nervous gan- 

 glia ; and during gestation it has been ascertained that the nerves, like the 

 vessels, enlarge, and after parturition return to their former size.) 



Development. — Narrow in the foetus, and in the adult which has not been 

 impregnated, the uterus increases in size in animals which have had young 

 several times. 



Functions. — The uterus is the sac in which the embryo is developed. 

 The ovulum grafts itself upon the mucous membrane of the organ by its 

 placental apparatus, in order to draw indirectly, from the maternal blood, 

 the materials for its development. This function of the uterus gives rise 

 to most interesting anatomical and physiological considerations, which will 

 be referred to when giving the history of the ovum. 



4. The Vagina. (Figs. 411, 412.) 



The vagina is a membranous canal with thin walls ; it succeeds the 

 uterus, and terminates posteriorly by an external opening — the vulva. 



Situation and Relations. — Situated in the pelvic cavity, which it passes 

 horizontally across, the vagina is in relation with the rectum above, below 

 with the bladder, and laterally with the sides of the pelvis and ureters. 

 Loose connective and adipose tissue surround it posteriorly. 



Internal conformation. — The inner surface of the vagina is always lubri- 

 cated by an abundance of mucus, and is ridged by longitudinal folds {co- 

 lumnx rugosce). In front, at the bottom of the canal, is observed the 

 projection formed by the cervix uteri ; posteriorly, this surface is continuous 

 with that of the vulva. 



Stedctuee. — The vagina is formed of two tunics ; an inner, mucoas,. and 

 an external, muscular. The mucous memhrane (pale-red in colour) is con- 

 tinuous with that lining the vulva and the uterus (and bladder) ; it is 

 provided with papillas, and is lined by stratified pavement (squamous) 

 epithelium. (It consists of connective and elastic tissue, to which its 

 extensibility and firmness are due.) 



The muscular coat is rose-coloured, and traversed by a large number of 

 vessels ; it is surrounded, for the greater part of its extent, by an abundance 



