884 THE APPARATUS OF GENERATION. 



to propel that organ outwards, especially after micturation ; in this case, the 

 fibres of the constrictor attached to the clitoris erect it by its base, while 

 those which are fixed into the skin between the thighs depress the inferior 

 commissure of the vulva. This double action necessarily exposes the 

 erectile tubercle lodged in that commissure. 



ANTERIOR CONSTRICTOR OF THE VULVA. Analogous to Wilson's muscle 

 in the male, this constrictor is formed of arciform fibres which envelop, 

 below and laterally, the vaginal walls at the entrance of the canal; its 

 extremities are continued, by means of aponeurotic fascia, to the sides 

 of the rectum, where they are lost. By its posterior border, this muscle 

 is mixed with the preceding. 



4. Muscular ligaments of the vulva. Traces of the suspensory cords of 

 the male penis, these ligaments are disposed in the same manner at their 

 origin. After becoming united beneath the rectum, they descend in several 

 fasciculi into the labia of the vulva, and disappear among the fibres of the 

 posterior constrictor. 



5. External skin. This is fine and black (or light-coloured), destitute of 

 hair, smooth and unctuous, and adheres closely to the subjacent tissues. 



6. The Mammce. 



The mammce are glandular organs, which secrete the fluid that should 

 nourish the young animal during the early months of its life. They are 

 rudimentary in youth, and become developed with the advent of puberty, 

 assuming their greatest development towards the end of gestation ; they are 

 most active after parturition, and cease their function, as well as diminish 

 in volume, when the period of lactation has terminated. 



Situation. These glands are two in number, placed beside each other in 

 the inguinal region, where they occupy the situation of the scrotum in the 

 male. 



Form. They are two hemispherical masses, separated from each other 

 by a shallow furrow, and showing in their centre a prolongation called the 

 teat, nipple (dug*), or mammilla, which is pierced at its free extremity by several 

 orifices for the escape of the milk ; it is by this prolongation that the young 

 animal effects suction. 



The two glands are fixed in their position by the skin which covers 

 them, and which is thin, black, covered with a fine down, and altogether 

 destitute of hair in the vicinity of, or on, the teat, where the cutaneous 

 surface is smooth, greasy, and supple. They are also attached to the 

 tunica abdominalis by several wide, but short, elastic bands, which resemble 

 the ligaments of the sheath in the male. 



STRUCTURE. Structurally, the mammary glands offer for study : 1, A 

 yellow (elastic) fibrous envelope; 2, Glandular tissue; 3, The galactoferous 

 reservoirs or sinuses ; 4, The excretory canals or mammary ducts. 



The elastic envelope, placed in the middle, beside its fellow of the 

 opposite side, is mixed with the suspensory bands that descend from the 

 abdominal tunic, and sends into the substance of the gland a number of 

 septa, which are interposed between the principal lobules. 



The glandular tissue is a compound of gland vesicles or acini, clustered in 

 groups around the lactiferous ducts. (The gland vesicles are made up of 

 an amorphous membrane, membrana propria, lined with spheroidal nucleated 

 cells. They are about l-200th of an inch in diameter.) The lactiferous 

 ducts commence by blind extremities, and run into each other to constitute 



